14 days off and all lifts improved.
I know many people have adopted more of a modern take on Mentzer's philosophy (training a muscle once every 7 days with 1 or 2 sets per exercise).
I tried this and couldn't keep up. Training to failure makes my system take a beating and some lifts improve while some stagnate or get worse, so it's always a gamble.
Recently, I tried the "after two weeks off, you come back stronger". Did this with legs a few weeks ago, and now did it with upper body. ALL my lifts improved and I felt fresh when arriving at the gym. I'll keep 1 or 2 sets per movement to absolute failure tho.
The question is probably: do strength gains translate well to muscle growth at such low frequency?
I've also incorporated cardio. No longer getting winded by going upstairs or after lifting. I'm doing both aerobic and HIIT cardio, to cover everything. I use the bike station. I know it's off-topic, but wanted to say it.
Mentzer was innovative, to say the least.