The 16F84A has a typical endurance of 10,000,000 writes.
It seems like a big number, but if you write every 100ms, that EEPROM location will stop functioning in 11.5 days.

Of course, that's the "typical" endurance. The minimum endurance is 1,000,000.
So it could stop working in as little as 1.1 days.

It would be a good idea to slow it down considerably.