Mimulus

I've often thought about sowing annual mimulus but then read that it likes damp conditions and discounted it because I'm on stony flinty dry soil.  Now my pal who does not garden has a couple of pots of yellow and orange mimulus on her quite sheltered patio that she says come back every year.  When I asked if she did anything special with them she just looked at me quizzically and asked 'like what?'  So she gave me a small root of each and they are now filling 8" pots in the GH.  Common sense says they'll be ok in there over winter without much attention,  what's your opinion?   Are there different  varieties, i.e. annual and perennial?