I can't speak toward the rest of the advice here, and my 30" belt sander has ACE hardware belts that are too cheap and disposable. However, on my shoemaking rollers, I have to cut a strip off a roll of various belt grades every so often and replace it on the wooden rollers. I use contact cement, and my advice is this;
If you do use contact cement, it works best on roughed up surfaces where applied to both surfaces and dried with the heat of an ordinary light bulb...say five to ten minutes or so... You get one shot at putting the surfaces together ( such as the two billets of your belt) but that joint is likely to hold for a good long time, especially when pounded by a rubber mallet.
Hope this helps and,
Don't shoot yore eye out, kid
The Capgun Kid