I live in a 90 year old apt. building in NYC. Dimmer switches were added, by previous owner, about 8 years ago. Recently, the dimmer switch for bathroom ceiling light (flickered; changed the switch and it now works fine), bedroom ceiling dimmer switch (doesn't dim; only bright) and switch for trash disposal (must hold switch "on) all broke. Is it possible the three issues are connected? It seems odd that three unrelated switch issues should happen around the same time. Should I consult an electrician?

I will suspect the three switches are worn from normal use, and all failed as a coincidence. I cannot imagine any type of issue that would connect all of these failing around the same time.

Consulting with an electrician that will visit and examine all three may be wise for for piece of mind.

I agree but I have seen some disposals that come with a switch that must be held to keep the unit running, it's a safety feature. http://www.drillspot.com/products/582233/pass_and_seymour_tm870stmwcc6_15a_wht_gardisp_swit ch?s=1&catargetid=1623454804&gclid=CMTbgYHH4bMCFctcMgodFxkA6g