Depends on what minidisc recorder you have. My Sony has "MDLP" which apparently allows me to record up to 4 full length cd's onto one MD. Of course if you are taping on a newish recorder, it might well not playback on an older MD player. I'm sure even the older recorders allowed one to store more music onto an MD at the loss of stereo. Otherwise, MD's have 74 minutes capacity as far as I'm aware.
really does depend on the length of each track...normal usuage should allow 13 tracks okay. to be honest, I prefer to have one album on one disc in anycase!
The mini disc i use to have says it could fit 4 albums if recorded LP mode.But i thought that was the case as long as all the cd's had the same number of tracks.