This may be a stupid question, but with front projectors, will you still burn the screen with different aspect ratios?

This depends on the type of projector.

If the projector uses cathode-ray tubes (some do), then yes you will still get burn. If the projector uses DLP or LCD, then it won't burn.

See, the whole thing is: "Burn" is a misnomer to begin with. The correct technical description should be "uneven aging of the phosphor material".

The phosphor on a CRT is a consumable. It gets dimmer the more it's used. So if you constantly watch TV with black bars in the same place on the screen all of the time, then those areas of the screen won't "age" as fast because they're not being used much. Similarly, if you watch the same TV station with a bright white logo bug in the same spot on the screen all of the time, those particular pixels will age faster than the rest of the screen.

And honestly, if manufacturers would just use gray bars instead of black bars when letterboxing or side boxing, and if TV stations would move and change the logos often enough then you wouldn't even burn the CRTs either.