Superlow springs tend to kill shockies very quickly. My guess is that your shocks have RIP-ed and hence hitting the bumpstops very quickly. In addition (like what you said), springs sag as they age and thus adding to the problem.

Personally, I think superlow springs are not advisable as they offer very very little travel before hitting the bumps. This translates to poorer at-the-limit handling, reduced shocks longevity and a harsh ride. Then again, to each his own, some rate the slammed look higher than the practicality of things.

Being an 00, I would venture to guess that the mileage will be a little on the high side. I would take this opportunity to upgrade the shocks as well. Having said that, coilovers are much cheaper than they used to be, so maybe look into that as well.

And then braces, bars, bushes, links, oops.. got carried away