If the bulb says 55Watts right on it that should be okay for the time you said, yeah.

But if it is a compact florescent - then the 55 Watt part might be a number for what kind of regular incandescent bulb it is going to equal.

The package mighta said "equal to" or "replaces" a 55 Watt.

That might mean it could be weaker than you want, even for the first couple of weeks. Does it say 55 Watt right on the bulb glass?

Is it a CFL (compact flourescent) or a regular flourescent?