Gary is right....if you are performing at a Restaurants, like in most places, they have regular patrons....you do NOT want to play the SAME songs over or repeat them frequently...and in MY opinion, the songs should last 3 to 3 1/2 minutes....(in terms for pros.....radial time), unless is a meddley.
I perform in the Phoenix area in "Tea dances", special events, Restaurants and the people notice that I do not repeat songs often.....Is one of the biggest mistakes most make, you want to keep "fresh" the music to your audience, and do it also for yourself, at least, I also could get bored with my own music...but I don't let that happen, I play perhaps the same song, but I do not use the same style, alternate various styles, key, in a meddly formats, etc.... I also try to remember what songs I play in everyplace...I can remember music, not phone numbers or names...well, there are many different ways to keep music FRESH. My repertoire is somewhere around 600 songs on ALL types, styles, tempos, time lines...etnic, dance, slow, medium, fast....etc.