>>715117424 (OP)There absolutely is a right time.
Futureproofing!
You see, components on the motherboard can be dated rather quickly. Once there was IDE hard drives, now there's NVME hard drives. Once there was a DDR RAM slots, now there's DDR5 RAM slots. Once there was AGP slots for GPUs, now there's PCIe slots. None of this is even including the CPU socket, which changes damn near every year.
Do you see the picture? If you buy a motherboard now with DDR5 when DDR6 is around the corner, you're shit out of luck, you'd have to buy a whole new motherboard and cobble your PC together again. Is it doable? Sure, but it's a huge pain in the dick.
HOWEVER!
Knowing when these advancements will take place is tricky, and first generation hardware with these new components might not be the best quality.
Really though, the right time to get a new PC is when the one you got now won't do what you want it to.