Drive it steady (off boost) for first few miles to let oil temp come up (takes longer for oil temp to come up than water, so just cos water temp gauge is ok doesn't mean oil is). Drive it steady last few miles to let ALL fluids circulate and cool evenly.
Any other time, loud pedal free for all :) I would advise getting an oil temp guage, impreza engines run hot and oil temp can kill the engine.
Friend of my thraped living fook out of his car for 80,000 miles, didnt blow the engine, but he always warmed it up, let it cool down and car was maintained no expense spared. Car finaly had enough when pin balled off 3 trees, but he walked away unhurt.