Beginner question about growing E. coli
The higher the temperature the faster E. coli will grow, with a maximum growth rate around 37 Celsius.

If you grow E coli at lower temperature, the ecoli will grow slower. 

At 37°C you will see colonies overnight (16hr). 

At 30°C you will see colonies in about 1 and a half days. 

At 25°C you will see colonies in about 3-4 days.

You can do experiments at room temperature, but you will be waiting for days for what you will normally see after a 37°C overnight incubation.

As for satellite colonies.. yes ampicilin does break down with time and water. You can solve that problem by increasing the amount of Amp you are using from 25ug/ml to 100ug/ml. Or use 75ug/ml Carbenicilin. Or change your selection markers and use a more stable antibiotic like Chloroamphenicol.