Changed 95% of the water, when is cycle complete?

[Computer Prog]

My 10 gallon tank is about 10 years old and my last batch of fish just
died off due to ick and some sort of bacterial infection. The ick
developed after adding a few new fish.

I used a gravel vac to get out as much water as possible (about 98% or
so) but I did not remove the gravel. I removed and cleaned all of my
rocks & ornaments. I put all of the ornaments back and filled the
tank up using water from a Brita pitcher. The tank has a small
Whisper power filter.

I put a small dose of CopperSafe & Maracin in the tank and raised the
tank temp up to about 93 degrees. The tank got cloudy after raising
the temp but it cleared itself up after a few days. I let the tank
sit for a week with no fish and did a 20% water change. The tank got
cloudy again and cleared up after 2 days. I let it sit for another
week. I tested for pH, ammonia, and nitrite using a drop based test
kit from Aquarium Pharmaceuticals. pH was neutral and ammonia &
nitrite were zero. The tank looks spotless and the water is as clear
as bottled water.

I put two small fantail guppies in the tank and have been feeding them
very carefully. 5 days have passes and I just tested for pH, ammonia,
and nitrite. pH is neutral and ammonia & nitrite are still zero.

How do I know if this tank's cycle is mature? Should I be seeing some
ammonia or nitrite? I have been testing water samples taken right off
the top of the tank. Do I need to test water from the bottom?

[Geezer From The Freezer]

if you haven't cleaned your filter or gravel then our nitrifying
bacteria should be helping the cycle process along.

I think it should be fine. Keep monitoring your ammonia, nitrite, nitrates
if it doesn't spike, it is cycled.