Today, for my oldest laptop, the one I dedicated to office use, I marked each project it is attached to through BOINC to no longer receive tasks. As such it is my plan to retire the machine, and hopefully let it live out its remaining days peacefully. The real question is what prompted this decision?
For one I am not in a position to pump much money into old machines just to keep them working, in fact it has long been my plan that should that laptop die, I would make due without a computer while in my office. Not to mention while it has always been a noisy computer, I believe the bearings on the fan are starting to fail. Not to mention because it is such a noisy computer I often feel bad leaving it on and running when I leave the office for hours at a time, while my office mates may potentially be in the office, though they have never mentioned anything to me, so it can not be that bad.
As such I figure its best to keep the heat levels down somewhat naturally, as it's quite evident after crunching for about a year now that crunching causes a heck of a lot of heat.