Users can develop a tolerance for mushrooms however, as a result, it begins to require more and more mushrooms before the user begins to feel the effects. If a person uses them multiple days in the row, they are likely to experience a decrease in the quality of their high each day.

Those that use LSD, mescaline and psilocybin mushrooms may find that they also build up a tolerance to these drugs as well. Mushrooms are used less then other types of drugs. Some people won’t use them more then once.
It is possible to abuse psilocybin mushrooms however. Those who enjoy the experience may use them in great amounts and often, which can lead to a number of problems. 

http://www.shroomery.org/8769/Are-psilocybe-mushrooms-addictive