Total training time is a little over a year but I had to take 8 months off for an internship so I started BJJ around 2 years ago. The best advice I could give to a white belt is to never try to force techniques, learn to transition positions really well before you worry about subbing people, try to learn your techniques in chains, learn to completely let go of your ego and learn YOUR game.
I'll elaborate a bit on these:
1. I struggled with not using my size and strength with people at first. I didn't have much technique but I was really big and powerful then because I had just retired from powerlifting. So, when I was rolling with someone who was beating me with superior technique, I would fight back (and a lot of times I would "win") with my superior physicality. As time went on I realized that this was holding me back from getting better at the techniques which is obviously the goal of training. Slowly, my strength has gone away and I have replaced it with technique which is sooo much more effective and not nearly as tiring!
2. I didn't really have an issue with this but I noticed that a lot of white belts want to learn the coolest, flashiest, most complex submissions. This is pretty ridiculous if you still can't sweep someone in your guard, escape side control, etc... You cant submit anyone if your positions suck so get those squared away first. Then learn how to transition between those positions and maintain them, then add submission techniques. Just try to learn things in an order that makes sense. Get comfy moving from bottom side control to half guard, to closed guard, sweep from closed guard, pass the guard, establish side control, mount, knee on belly, kesa gatame, north-south, back to side control.... after you can do that well, setting up submissions is tremendously easier and more effective.
3. A lot of people know a bunch of techniques but they can't tie them together so they might as well know nothing at all. Imagine you know an armbar from mount, a rear naked choke and a guard sweep but you are in top position half-guard. What the hell would you do? Now imagine that you are in half guard and you know a half guard pass, a transition to kesa gatame and a basic sub flow from kesa gatame like leg americana, straight armbar, head and arm choke. Well, your training partner would be in for a rough 5 minutes!
4. Most importantly, understand that "winning" in bjj doesn't mean kicking everyone's ass; it means getting better at grappling and sometimes you have to take ass kickings in order to do that. Sometimes you need to drill a technique 500 times before it clicks. Sometimes you have to try a new technique and fail over and over and over.
5. Lastly, you will find a certain game that really works for you and just feels natural. For me, that game is getting to and subbing from kesa gatame. I knew it the first time I got someone in scarf hold. Some guys have killer bottom guard games, though, or are great at attacking from deep halfguard and x guard. Those same guys couldn't play my kesa gatame game like I do just like my guard game is weak sauce compared to their's. Make YOUR own bjj.