i have a plastic dyno saddle that i've had on a number of BMX bikes since like '88. it's kinda of a gag now that i have to put it on every bike and rock it for the first few days, mostly since i've had it so long (DAMN! about a month or so shy of 20 years!!!) and it's never gotten tossed or broken.

it seriously hurts my gooch though after about 5 miles.