They last as long as you're willing to put some time in for basic maintenance and repair. So yes, easily last 15 or even 20 years.
Many people don't last that long for a variety of reasons. The new rigs are much better laid out than units 10 years old or even 5 years old. Wasn't that long ago where having 1 slide was "WOW!" and now we have 4 or 6 of them sometimes.
So long as you'll invest your time to fix the little things like keep the roof and windows sealed or replacing a failing AC or converter (which is really pretty simple) the unit will last for you.