I have a single user well (not a well share) and was dismayed to find air in my lines. It seam that one of three things is happening. 1) One way valve on the pump has gone bad 2) well is going dry 3) i have a leek in my pressure cylinder. I figure since my pump is 5 years out of warranty it might be time to replace it or upgrade. I have done a lot of research and have looked at Simple Pump Solar and similar as a replacement; what are you thoughts? the problem is so bad I have to bleed the air off at the sediment filter everyday.

Sounds like the bladder in your pressure tank  has a hole in it. Replace the pressure tank

The pressure cylinder is very lite. Is that due to the air escaping from the bladder and not allowing water in?

Its been my experience that when you get a hole in the bladder the tank gets very heavy as it becomes water logged. If it is lite or as little water in it your check valve may be bad and allowing the water to drain back out in to the well. How about a little more info on your system is it a submersible pump that is down the well or a jet pump in your house