Hey there Jeki,
It sounds like you are running into an issue where after some time the connection over Back to my Mac is timing out. I recommend these troubleshooting steps from the article named:
OS X: Using and troubleshooting Back to My Mac with your iCloud account
Troubleshooting Back to My Mac
If Back to My Mac is not working as expected, try the troubleshooting steps below, if they apply.
- Update all your Macs to OS X Lion v10.7.3 or later (OS X Lion v10.7.4 or later is recommended).
- Choose System Preferences from the Apple () menu. Open iCloud System Preferences and check that Back to My Mac is enabled. See if any diagnostic messages are provided under the Back to My Mac section to assist you with troubleshooting and resolving any connection issue.
- Toggle Back To My Mac off and back on by deselecting and then reselecting Back To My Mac in iCloud System Preferences.
- Make sure the computer you are trying to connect to is not sleeping and is set to Wake on Demand. For more information about Wake on Demand, see this article.
- If you are using an AirPort base station, make sure your firmware is up-to-date (open AirPort Utility 6.0 or later).
- Check your network for a multiple NAT setup and reconfigure your network as needed.
- Make sure NAT-PMP or UPnP is enabled (if you are using an AirPort Extreme Gigabit Ethernet base station, click here for information about AirPort Extreme Gigabit Ethernet and NAT PMP).
- Ensure TCP port 5354 and UDP ports 4500 and 5353 are open on your firewall. To learn more about ports used by Apple products, click here.
And this if needed:
If you still are unable to use Back to My Mac reliably
Contact iCloud Support. Be sure to provide the following information:
- A detailed description of your network setup for each computer, including router types or models and modem brands.
- The details or screenshots of any diagnostic messages provided in the Back to My Mac System Preferences pane. (For assistance with screenshots, see this article for OS X Lion or this article for OS X Mountain Lion.)
- The results of the traceroute performed on each computer when checking for a multiple NAT setup. (For assistance with capturing the traceroute, see this article for OS X Lion or this article for OS X Mountain Lion.)
- The Computer Name and Local Hostname of each of your computers.
- Any other troubleshooting steps you have performed.
Thank you for using Apple Support Communities.