Your Mileage May Vary…
Aerosol cans may last for up to five years, depending on more variables than you can shake the can at. Best thing to do is shake very thoroughly (If you can't get the aggitator ball loose, throw the can out.) and try a test shot. Any serious problem will become immediately obvious or will show up in the cured coating.
As for the Testor's and MM paints, you didn't say whether they were enamels or acrylics. MM acrylics are not the best for long term stability.
In either case, open the bottle and stir thoroughly. If, after five minutes of stirring there are still blobs or lumps, throw it out. If at any point you notice stringyness, throw it out.
Assuming it passes the above, once thoroughly stirred, put a dab from the stirring instrument on a scrap of clean styrene. If, after curing, it looks good and doesn't scrape off, the paint is still good.
Tube glue is history at that age. Solvent cement, like thinner, is fine as long as it is liquid. I doubt if cyanoacrylate glue, unless kept sealed and refrigerated, will last that long (none of mine has).
Filler is essentially the same as paint: if it is still formable and hardens, it's fine. Some fillers, allowed to sit for that long, will separate. If you can manipulate it in the tube, that will help mix it back together. If you can't, then it is obviously no longer usable.