First, congrats on thinking about this well in advance.
Second, if you can consistently put in 300 structured hours per year, I think you’ll be ahead of the typical climber out there that recreationally goes by feel.
I recommend using the guidelines in TFtNA as a template for each year’s training. Scale the hours and proportions per intensity so that it fits into a 300-hour training year. Have intermediate objectives to train for each year.
If you can stick with a structured plan, you’ll see gains. However, at some point, 300 hours won’t be enough anymore. Once you adapt to that volume, it will become maintenance. All athletes have to gradually, continually increase the stimulus.
At that point, the temptation will be to add a greater proportion of high intensity training into the mix to make up for the volume you need. Many think of it as making up for lost time, but don’t get sucked into it. In reality, it makes your fitness live on borrowed time.
I doubt that the average climber gets in 300 hours per year, so you’ll be well ahead of the game. Just make a plan and stick to it, and follow the TFtNA guidelines for what to do when.
I hope that helps.