Is there a way to temporarily prevent my phone from locking / sleeping?

No app needed. Go to Settings > General > Auto-Lock, and change the option to 'Never'. When you're done, change it back to whatever you normally use.

There is not, and there will be no 3rd party app for this since 3rd party apps don't have access to private iPhone API's for security reasons which such a 3rd party app would require.

Here's a hint. If the only app you can find to do what you want requires the iPhone to be jailbroken, then there are no legitimate Apple-approved apps to do what you want, and there's a very good security reason related to why.

Is it really that long of a process?

1. Tap Settings.

2. Tap General.

3. Tap Autolock.

4. Tap Never.

If there was an app that allowed this, how would it go?

1. Tap the App.

2. Wait for it to launch... (Preinstalled apps almost always launch faster than third-party apps)

3. Tap whatever option to disable the auto-lock.

You're literally talking about a few seconds. I understand your point about wanting an 'easier' way to do it... but I just don't agree that there's any level of inconvenience, nor that a third party app would make it easier or faster.

I share fehrman's interest in an "easy one-click option" for suspending Auto-Lock. It's an issue for me when I cook from a recipe, but also when I'm timing something with the stopwatch. I could see it as an on/off toggle in the Control Center, though that's obviously highly contested real-estate. Perhaps even better than a simple toggle, though more complex, would be a temporary suspension of Auto-Lock that times out after an hour (though that could be overridden. I'm sure I'm not the first person to forget to re-enable Auto-Local and erroneously conclude that my battery life was mysteriously decreased.

In addition to it being annoying to do this everytime you cook (or in my case using a dice app with students as part of an educational game), you need to remember to re-enable autolock when you are done with the activity. It would be so much better if you could simply temporarily suspend autolock, for X minutes. I really wish Apple would provide this option. Wouldn't be a big deal to have to go into settings to do it, if you didn't have to remember to go back and undo it when you wanted autolock to resume.

I agree with fehrman and others who have expressed interest in a 'toggle' like feature to turn on and off the Auto-Lock function. At the very least, an override function based on specific apps. My use case is around phone calls, as the iPhone is my primary work device. As a courtesy, I mute the phone when I'm not talking. I'll turn Auto-Lock to 'Never', so I can unmute quickly if asked a question. Since I may be on back-to-back calls, at the end of the day I forget to reset it to 30 seconds and quickly run down the battery. A Phone app override that would 'disable Auto-Lock while on a phone call' would increase usability and be extremely valuable to prolonging battery life.

For me, it is not laziness, it is knowing that I will probably forget to put it back to where I had it, which could be dangerous. I actually have one app that keeps the phone open while I'm using it. I do wish most apps would have the same option. I find it most annoying (it locking) when I am installing updates (even Apple ones) and it stops because it locks. I really think there should be an option to just temporarily keep it unlocked (until, say, you close the app you're using) then return to the normal settings. Can't be that hard, surely?

However, if you have corporate email that requires a phone that can lock, these option for Never is disabled. I really need an option to temporarily disable it.