I can't help you with the paint issue, but be aware of the fact that aluminum fatigues very differently than steel. The engineering term is "yield". When steel yields, it bends and takes a new permanent "set," but doesn't come apart. When aluminum yields, it just breaks clean through.
The aluminum in a beer can is soft. The aluminum in bike frames is very strong, but brittle. Metal fatigue is cumulative; an aluminum frame comes apart or breaks down a little every time you ride it. So does steel, but again steel bends, aluminum breaks. Eventually an aluminum tube or weld will fail catastrophically and break clean through. At speed, this type of failure will result in a very bad crash.
The point is that 5 years is a lot for any frame and especially aluminum. You don't want to be blazing down a hill at 35 mph and have your top tube or downtube separate from the head tube.
Frames and other non-steel alloy components should be retired well in advance of their failure. This means aluminum and titanium seatposts, dropouts on forks, steerer tubes on forks, stems, bars, bottom brackets and especially cranks.
Whatever you do, never use titanium bottom brackets or pedal spindles. As someone who has broken a bottom bracket (Dura-Ace) during competition, I was grateful it was steel and not alloy. The steel yielded slowly, almost in slow motion, and this gradual failure over 1-2 seconds allowed me to thankfully keep it together and not crash. If I were using a ti B.B., I would have crashed hard. I've also cracked Dura-Ace cranks. I continue to use and love Dura-Ace cranks and bottom brackets because they are the srongest!!!
If you are big or strong and especially if you are big and strong, retire frames and components sooner than lighter or weaker riders. Regularly inspect your entire bike (manufacturers suggest before every ride) and especially high stress parts (cranks) and all welds.
Good luck!!!
