Everyone's circumstances are different.My criteria would be if you are not shorting your family buy what ever you want within your means.
I always have wants,I rarely have needs.My thing is having top quality stuff,once I have it though I will stick with it until it no longer does what it is supposed to do.I have one bow that I have had for 5 years now,I have a simple battery of rifles,a 22,a 12 guage,a .270,a 30.06,a muzzle loader.I drive a 10 year old Toyota Tacoma.
I am fortunate in that I can afford to do much more than I do but my sense of value and my sense of personal responsibility keeps me from purchasing the lastest this or that.
My current focus over the last couple of years has been quality clothing for all my hunting scenarios's.I am two or three pieces from being done with that and then I wont likely be purchasing any thing for quite a while.
If your weapon is reliable and you are clothing is comfortable then you can place all your focus on your hunting.Thats how I view it.
I think Scot has it right. The key factors here seem to be twofold:Waste and Opportunity Cost.
I guess it's not "opportunity cost" in the purest sense, but it's still a forgone opportunity to spend money elsewhere sensibly. To put it frankly, I know guys who live in run-down single-wide trailers, but drive $35,000 pickup trucks, own $5000 ATV's, have $1100 bows, and their kids look like refugees - wearing 3rd generation hand-me-down Walmart clothes with Kool Aid stains on their bellies.
Call me snotty, call me what you want, but that bothers me. Kids should be priority one. Instead of blowing $40-50,000 on a vault of guns, bows, ammo, camo, pickups and quads, how about buying a modest used pickup truck, keeping only a skeleton crew in the gun cupboard, using an older (but still reliable bow)? Use the extra $30,000 on building a home for your family. Maybe buy the kids some new clothes. Teach them the value of a dollar. I just have a hard time swallowing it when I see guys neglecting their own children to fund their lust for hunting, pickup trucks, entertainment, ATV's, etc...
Waste: There is a degree of waste involved if you're scrapping one 3-pin sight (that you bought last year) - and replacing it with a new 3-pin sight (that you bought this year). Again, if you can afford it, and your primary responsiblities are met, then that's fine. Stupid, but fine.
Same goes with bows. Not much point in peeing away $700 to buy an 07 one-cam that will shoot 287, when you have an 06 one cam that already shoots 287.
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There are real situations when you can use an upgrade, but those "upgrades" should be made with your priorities in mind. It just leaves a really bad taste in my mouth when I see people blowing money to fund their own vices (in this case, the vice is bowhunting) at the expense of their family (kids in particular).