Toyota Repair: 95 Toyota Corolla - periodic no-start, toyota corolla, starter relay

Question
95 Corolla 1.8L with 78k miles.  Periodic no-start.  Clicks and power to accessories, but no turn-over.  Have had it towed 4 times to mechanic & even dealer, but starts fine when it gets there.  Left it there 3 days, always started for them - then drove it home and it would'nt re-start.  

Sits for a while, sometimes starts.  No pattern (when it starts, can drive it for several days without a problem - other times can start it and drive 1 mile to the store and it won't re-start) but now it won't start at all.  

I hate to keep towing it just to have it start when it gets there.

Replaced battery, starter and starter relay previously.  Someone suggested replacing the ignition lock (my wife is one of those with a "huge" keychain with everything including the kitchen sink attached)as there could be bad contacts in the cylander due to the constant abuse from the keychain.  

Any suggestions?  

Answer
If there is a clicking noise it means that the starter is getting a voltage to the solenoid terminal, I doubt if the switch is the problem, if it was the starter wouldn't make the clicking noise, it is very possible that the starter is the problem again.