The OP's question has, I think, been given a few different and good answers, so I don't feel guilty about this thread derail.
I get a lot of people who've "done Starting Strength" for 2-3 years on their own. The women are usually up to squatting 50kg or so, the men 100kg or so.
It's not possible to do Starting Strength for 2 - 3 years and remain at that level. The weight increases go up so quickly that most people have to stop the program from 3 - 6 months.
Notice the quotation marks. I'm reporting what they
told me. When we delve into their journals, if they (rarely) have one, or more commonly their memory, what we usually see is: started the weights too high, got stuck, stopped for a month, started again, got elbow tendonitis, stopped for six weeks, started again, got hip flexor tendonitis, stopped for a bit, built up, got scared of the grind and "backed off to work on form", and so on.
This is indeed
not doing the Starting Strength novice progression. But they
tell me "I was doing Starting Strength for 2-3 years." Likewise: power cleans are in the programme, but almost nobody does power cleans on their own. More similar insights in
this article - like I said, most people start too high and give up early on, etc.
For example, someone in this thread reports squatting 225 after a month and 285 after 12 months. If after a year he'd done 405 then 225 after a month makes sense, he's just a talented guy, maybe a 250lb Samoan or something. But if after a month he gets 80% as far as he got in 12 months, then he started too high. This is no slight on the guy, it's a very common issue - because the book, the site etc don't specify the starting weights. It'd be better to just err on the side of caution and say "start with the empty bar, add 5lbs a time", then you hit 285 in 4 months instead of 12 (because you got no injuries and took no breaks) and will find you can surpass it.
But it's hard to persuade a young male to start with the empty bar. It's also hard to persuade them to stick with training once the weight gets heavy and there's a grind; women stick with it better. In my gym they do 3 month terms. 2/3 of the women but only 1/3 the men go for a second or later term. They hit around a 120kg squat and say something like one of the following:
"Actually I'd like to work on my cardio."
"Work's getting pretty busy."
"I need to spend more time with my family."
"The commute is getting hard."
These are all legitimate concerns. Cardio is important, we have to work, family comes first always, and I hate commuting so much I work from my garage and was actually upset yesterday that I had to walk the 20 steps in the rain. But... when they squatted 60kg they didn't care about cardio, work was fine, they were happy to ignore their family, and the commute wasn't an issue. Now it's 120kg these are all serious issues. Funny that.
Hardly anyone goes further on their own uncoached than they do in 3 months in our gym. And just generally, not many people go further than they got in 6 months - by that stage you need to be pretty dedicated to it all, have no interruptions due to holiday or work or sickness, etc - progress is for the truly dedicated and lucky. I know you don't get this impression from trainer websites, apparently everyone's squatting 400lbs in 3 months. Well, it's like this: for every 6 people I train,
1 will get awesome results, like the woman who squatted 115kg in her first 3 months
1 will get shit results, like the guy who squatted 100kg after 12 months
4 will get mediocre results, like the women squatting in the 60s kgs after 3 months.
Guess which one we trainers will talk about on the website, and which ones we try not to mention? And if you're a weight loss trainer you talk about the 400lb guy who ended up with sixpack abs, you don't talk about the 300lb guy who's now 350lbs. Now, I talk about them
all, but I'm terrible at marketing.
Reality. Sorry, but there it is.
Anyway, with coaching any healthy woman under 50 can in 3 months squat 60, bench 40 and deadlift 80kg, and the guys can do 100/75/120. If they have zero physical activity history, eat badly and miss some sessions then they might do them as heavy singles, if they have some training history, eat well and show up all the time no matter what then they do 10-20% more. And you know, that's actually not bad if you're just lifting for health. You don't need to squat 400lbs for your health, past 225 or so you do it just because you like it.
On their own the 3 months becomes 2-3 years - for the few who keep lifting that long. The world is full of people who used to squat 500lbs until they took an arrow to the knee.