Don't forget that even 72 days of fallow and diligent quarantine only gives you 99.9% probability that your system is ich free. There is always a tiny risk left that is somehow found a way in.
100% certainty exists only in a tank filled with bleach.
Everything you do needs to be evaluated risk versus reward. I consider a 99.9% probability of being ich free (only a 1 in a 1000 chance of failure) pretty good odds, considering all the other unknowns and intricacies of this hobby that cause things to go wrong. Without being proactive (such as TTM for fish, fallow period for everything else that is wet) your odds of being ich free significantly diminish.