How to correctly communicate or express these timely sayings in French? "Do something while the conditions are right" or "Seize the opportunity when it presents itself"
Is this acceptable? Faites-le tant que vous le pouvez
The very same metaphor exists in French since at least the 14th century and is still in common usage:
Il faut battre le fer tant qu'il est chaud.
The preposition might be tandis, quand, pendant, or tant.
Pendant was most common in the 20th century but tant seems to take a small lead in recent years.
Your attempt Faites-le tant que vous le pouvez doesn't convey the same meaning. It's more like "Do it as long as you are able to do it."
You might say instead:
Faire quelque chose lorsque les conditions s'y prêtent.
Profiter d'une / saisir une occasion2 quand elle se présente.
1 Instead of occasion, the word opportunité is often used to translate "opportunity" but is sometimes considered an anglicism even while this meaning already existed in French (See the OQLF).
The dictionary Le Petit Robert 2006 gives a French idiom (under the entry "battre") that corresponds exactly with the English "strike the iron while it's hot":
Battre le fer pendant qu'il est chaud: profiter sans tarder d'une situation propice.
In other words: taking advantage of a favourable situation without delay.