Keep in mind that some sealers are combustible, so be sure and remember this if you ever have to have your tires worked on. Seems I remember someone getting hurt or killed fairly recently working on a wheel with the tire still on it when it had tire snot in it. (sorry, slime) /w3tcompact/icons/smile.gif In addition to that, some dealers, like mine will not take the tires in on trade or dispose of them...they bag them and give them back to the owner if they have new tires put on. It's not nice stuff to work with after it's in the tire...i've seen it.
I solved the same problem you had by having my filled with a gel sold by Agco called Soft-fil. Nice stuff. It fills the tire but doesn't leave it solid, the tire acts just like it was filled with air, but will not go flat for any reason...run over whatever and keep driving. It also adds weight to the tires, if i remember right, the front tires on my BX weighed about 45#s after filling. Cost is also a factor...the fronts were about $60 each to fill, but the results have been well worth it to me.