I just started snowboarding this year and I'm starting out on a Lamar. I've read that this board will be fine for a beginner but that I will outgrow it and at some point the board will limit my progress.
How will I know when that point is? What won't I be able to do on a Lamar that I'd be able to do on the NS Legacy? How do I know when I'm being limited?
When you start to get this bad itch of wanting a new board, then it's time. Until then, enjoy the Lamar!
Also, once you learn how to ride all the terrain, you'll start to notice things like board stability and edge hold. Your boards limits will start to shine through once your skill surpasses the board's limits.
Trust me you will get the itch. It's only my second year of boarding, and I am on my third board already. Went from a regular camber old school Salomon Surface > Sierra Reverse Crew > Never Summer Heritage. I could still be riding the Surface, but there's so many tempting possibilities out there that are hard to resist.
The Buy/Sell section on this forum are a great place to get a nice, minimally used board when you get the itch.
It's been 2 years since I last went snowboarding and I've only rented. I decided to get a good snowboard b/c I couldn't stand the rental ones anymore. They felt heavy and slow. It took a lot of effort to link turns and I couldn't keep up with my friends.
Best suggestion I can offer is to second what someone else already said and borrow a friends, rent a performance board, or try out demo days. You may not realize the board is holding you back until you have other boards to compare it to.
I rented a lot of different boards in my first years. I feel like I learned a lot from trying out various boards and I still believe the money was well spent.