Yeah. It's quite an individual thing and obviously NOT training because your lifts go up after a rest period, is not an answer.
They do say that for natural lifters that taking a week off now and then is beneficial.
This is the way anabolics are very advantageous over natural lifting.
The basic way they work is by letting your body use more protein etc and healing you quicker and better.
You lift weights, micro tears in your muscles occur. You need to to recover from that and you need to eat accordingly and rest plenty. A 3 day split is ideal for natural lifters.
On gear, lifters can work out 5 days on the trot and still recover especially if diet and rest is spot on. Arnie claims to have had only one day off and he has admitted to taking gear. I'm going to say he took 30mg of Dianabol a day as he's mentioned that gear in those doses and back then their doctors were 'treating' them with it.
Dianabol is very good at adding mass but it's slightly liver toxic in high doses. Most oral 'roids are.
So yeah, a temporary rest will do you good.