You're welcome.
Is there any harm in leaving my desktop Mail as is (POP account) and just realizing that I may experience an occasional "lock out"?
There is no harm with doing so, but I'm not sure why you would want to.
How do I release the email account from my iPhone?
There is no option for this.
I already have my data settings on the iPhone to "fetch" every hour--not to push. But does this apply to the IMAP account on the iPhone?
Push access for received messages applies to an email account that supports Push access. The following email accounts support Push access for received messages:
MobileMe
Exchange
A Yahoo account created with the Yahoo account preset.
"If" I decided to convert my desktop Mail account to IMAP, could I not just "add" the new account? Would I necessarily have to delete the POP account?
You don't have to delete the POP account, but you would want to make it inactive or disable the account with the Mail app - Mail > Settings > Accounts > Select the Account > Under the Advanced tab for the account settings deselect Enable this account.
If you want access to the locally stored messages in the POP account's Inbox and Sent mailbox with the iPhone's Mail app, you want want to copy the messages to a server stored mailbox or mailboxes after creating the account as an IMAP account.
Can I setup the account as POP on my iPhone and just keep it all POP? Or is this dependent on Charter's policies?
This depends on Charter, but I don't see why you wouldn't be able to access the account as a POP account with the iPhone's Mail app as well, but this will not get rid of the "locked out" problem on occasion.
A POP account is from the early dark ages of email account access with an email client on a computer when the overwhelming majority at the time had access to a single computer only - before there were laptops and laptops became mainstream, and before there were handheld cell phones much less cell phones in the smart phone category. Until the iPhone, phones in the smart phone category were primarily targeted and sold to the business/enterprise market, not to the consumer market. The iPhone changed all that - just look at all the copies and different phones in the smart phone category that surfaced after the original
Although it is possible to access a POP account with more than one email client, a POP account is designed to be accessed with a single email client only and includes a number of limitations that are not a problem with an IMAP account, which is specifically designed to be accessed with more than one email client.
There is no "locked out" problem with an IMAP account. You can store the account's Drafts, Sent, Trash, and Junk mailboxes on the server with the Mail app on your Mac, and the account's Drafts, Sent, and Trash mailboxes on the server with the iPhone's Mail app. The account's Junk mailbox stored on the server with the Mail app on your Mac will be available automatically when accessing the account with the iPhone's Mail app along with all other server stored mailboxes created for the account with the Mail app on your Mac or via webmail access for the account using a browser. You can transfer received and sent messages to additional server stored mailboxes by category with the Mail app on your Mac and with the iPhone's Mail app which will be reflected automatically with each email client. All server stored mailboxes are kept synchronized with the server automatically with each email client used to access the account. Sent a message with the iPhone's Mail app and the message will be available in the account's Sent mailbox with the Mail app on your Mac automatically and vice-versa. Read a new message with the Mail app on your Mac and the message will be marked as read automatically when accessing the account's Inbox mailbox with the Mail app on your Mac and vice-versa. Transfer a received message to a user created server stored mailbox with iPhone's Mail app and the message will be available in that server stored mailbox automatically when accessing the server stored mailbox with the Mail app on your Mac and vice-versa.
I keep the Mail app on my Mac launched and running 24/7 checking my IMAP account for new messages. I have the account's Junk mailbox stored on the server with the Mail app on my Mac, which is available automatically when accessing the account with the iPhone's Mail app and the same with my iPad 2. Any received message that is marked as junk and moved to the account's Junk mailbox stored on the server with the Mail app on my Mac is reflected automatically with the account's Inbox mailbox and Junk mailbox with the iPhone's Mail app and with the iPad's Mail app. The junk mail filter with the Mail app on my Mac is serving as the junk mail filter for the account with my iPhone and iPad as well - remotely since all server stored mailboxes with an IMAP account are kept synchronized with the server with each email client used to access the account.
NONE of this is available with a POP account.
If you have the option to access your email account as an IMAP account and you access the account with an email client on more than one computer or device, to me it is a no-brainer which way to go - IMAP, which is specially designed for this.