I can only speak from my experience with the Andro extender which is the one I use and if you stick to it for around 4- 5 hours a day it will give you results but it will take months and you might expect to see actual gains around month 3. At least that’s what the producer says and it’s when I started seeing results as well with around 4 hours on average of use a day.
If you make sure to add pieces to the extender arms a bit more frequently(as in making the extender longer, thus creating more extending force) you’ll might get away with wearing it for much less than the suggested 8 hours a day, because most people neither have the time nor patience to wear it that long every day. Heck you might even see results with as little as a couple a hours a day but it’ll take longer time all in all.
Also I’ve found that doing a short but effective manual routine incorporating A-stretches using a fulcrum, basic stretches and jelqing it’ll help ‘speed up’ your gains. At least it did so for me it seems. So not much need to add anything other than the A-stretches is what I’m saying. I do 6 sets of A-stretches and 6 sets of basic ones finished off with some dry jelqing. All stretches at 30 sec holds. And complete the whole routine within 35 minutes.
“There he goes. One of God's own prototypes. A high-powered mutant of some kind never even considered for mass production. Too weird to live, and too rare to die.”-Hunter.S.Thompson-
As long as a big can of Gillette shaving cream(7,5" or 19 cm), with picture proof in the 'full body picture' section. Pictures is the ultimate proof in the pudding, IMO.