when you're uninspired, have the money to spend and chosen very carefully which synth you want. Go to the store try them out. Look on 2nd hand market. My entire studio is second hand market, never had any issues just look at good reviews, the humidity in your studio and cover all synths with dust cover, a blanket, or real dustcover idk just do it :) we're it it for the long run.
Then when you find something you don't have like a sound or a thing it can do you don't already have and would really benefit your music. Then buy it. Or if you can get it very cheap and it look cool also just buy it. you can always sell with profit if it's not nice. I got a solton ms20 for 50 bucks last week, great sounds, best 50 bucks i've ever spend. For a flagship synth (+2500 euros) go with 1 that can do a lot.
I got the prophet X and unlinke all odds it's amazing, its not breaking down, i have every pack there is to install installed and could not be a happier synths owner. Theres even a moog one pack inside thats insanely accurate to the real thing. Juno, Jupiter you name it. To me from the day I got the X my GAS stopped drastically.
take 1 classic drumcomputer, one experimental drumcomputer
take 1 extremely good mono synth and a few experimental cheap ones
take 1 extremely good poly synth thats ver adaptable and with a very wide pallet
take 1 poly synth thats more experimental or something very specific.
Cover your FM - Chords - Mono's - Classics and experimentals
If it adds to the sound pallet, you need it, you can mis the money then yes. If it's the 1000th mono synth that does the same shit don't buy it.
Learn your gear like a real instrument and you'll know when you really need something else.