I've heard or some guys breaking them open to see what's inside. Even without the brittleness that comes with age, it would be a challenge to take the halves of the fusebox apart without breaking a bunch of the plastic. For starters, I recall that there are a couple of spots on the bottom of the box where the plastic from the two halves is melted together. You probably have to drill those spots out to separate the halves, and then you have to pry apart the two halves at all sides of the fuse box simultaneously as I understand it.
There are these copper connectors that slip on the contacts in the box which then connect the upper and lower halves. It sounded like those connections become loose over time. If that really is the problem, you could conceivably squeeze those little copper connectors a little to tighten up their connections and take any tarnish off them that has accumulated over their life while you're at it. That may not fix the problem though. Once the symptoms start, the heat could have started to damage the box itself with the added resistance in some of those circuits.
I replaced my box last month, and I told myself that I was going to take the old one apart to investigate. However, once the problem was behind me, I never looked back.