Whenever I'm pondering things like this, I ask myself why I'm doing it. I know that sounds stupid and obvious, but here's an example: many people sell their collections and such to 'get money they need'. But then you have to determine what that money will be spent on. I think it's a totally legit and mature thing to do when people sell their collections for the space and money a baby requires. On the flipside, if that money is just gonna go into your back account to slowly get chipped away at as you go out to eat and buy random knick-knacks, it's going to be a sad day when you realize you've sold something near and dear to your heart for random, arbitrary, and disposable things. There's also the time and effort you've put into your collection to consider. Many people spend years and years amassing a collection they're proud of. Do you really want to let it all go?
This is not to say that you're reasons aren't good. I don't know what projects you're working on, but if the money you'd get for your collection would really put a dent in the cost of them, then it may be worth it. This is especially true if you don't play them anymore.
That was a lot (sorry!) but I just know from experience that people sell their collections for money upfront and then really regret it later on.
TL;DR - Ask yourself this: "Is the money and space I will receive from selling my collection worth it, even with the amount of time, money, and emotional value I've put into it?" If the answer is yes, do it and have no shame! If not, I'm sure your collection will be happy