Very interesting question. I have a pretty utilitarian view of firearms at this point in my life, and tend to focus on filling niches that meet some need or direct interest. That seems to be what you're saying in your second and third lines. What do I need? What do I have a use for? Considering the relative costs of most firearms and related accessories, spending $20,000 a year could turn into quite a large pile of ... "stuff." Collecting things just to have a pile of things does strike me as a bit hollow -- that's just my own aesthetic.
I'd be likely to spend the money less on durable items and more on things that improve me personally. I like shooting and enjoy trying to learn and perfect it. I'd be likely to spend a large portion of that money on the costs of training and competition opportunities. A quest or challenge is much more compelling and fulfilling than an object.
Even in shifting your focus to personal development you may find the limits of the appeal. "Burnout" if you will.
That's often when folks begin to look at giving back. And not just generic "check-writing" forms of giving back, but personal involvement where money and items become tools to promote goals and enrich others. How is your local shooting or sportsmen's club doing? Can you convert some of your gun-buying budget into time to volunteer and/or fiscal support for their projects? If you've been trained to be a skilled shooter in one or more disciplines, can you teach others? Even just 4-H or Scouts? If the group is really worthy but limited (due to skills and/or funds), can you become more of a patron or possibly take on a leadership role to promote the goals of firearms, marksmanship, and RKBA education?
Lots of folks may get to a point in life where they're staring into their gun cabinet(s) (or garage, boat slip, etc.) at many thousands of dollars worth of "stuff" and just realize "so what?" and feel like they've wasted something valuable (time, money, effort). I believe far fewer look back on the efforts and funds they expended to share and made a difference to their fellow sportsmen and the next generation in the same way.