Granted it is about now I would start to expect to see them but the newer models (I guess you already know but jasper and maybe falcon and things after those) do well enough here, that said it is about now I would expect to start seeing failures here.
Dust it would be the big one.
You can do the 12V fan mod if you want though if you are modchipping it for RGH/JTAG purposes then you might as well use the software options that do effectively the same thing. Either way be prepared for an increase in noise.
Some might argue for doing the penny fix ahead of time.... it can definitely work if you are trying to bring one back but for beforehand I am not so sure it is worth it. To save looking the idea was tape up a few pennies (three or four depending upon the guide) and shove them in under the ram chips (under the motherboard)- it helps redistribute force and prevents the creep induced problems that cause RRoD.
After this we head into silly things territory (I was never convinced by shroud mods) and expensive things (ripping it apart and redoing the BGA to use a nice bit of lead solder).
On the slightly less expensive end I guess you could add extra fans but I am not sure unless you are going for the large fan, remove the DVD drive and so forth mods.
You might think about redoing the thermal paste and it might help drop it quite literally about 2 degrees; a lot of hassle for not a lot of gain.