" If done properly & maintained these
roofs should last 30 years. "
The problem with torch down is:  "have torch, will apply" and what company,
owned by what parent applied or supplied what, when?  I can't tell you how
many modified roofs I inspect that leak from day one.  And then it starts:
inspection, rep., contractor's site man, repair spec., repair crew, leak.
And what does the repair include:  web and tar for the sidewalls and reverse
laps for the low pitched areas...  and that is the 20 year roof the client
paid for?Material and application problems:  shrinkage, over heating, under
heating, etc.  However, not unlike patching mortars many of the basic
systems have advantages and disadvantages.
How do like foam?
Best,
Leland