This thread could give you some answers:
I've been a very happy VaM user for well over a year. I use it in VR through a Pico 4 headset and Virtual Desktop. I generally get great, even breathtaking results. But something I've noticed seems weirder and weirder the more I think about it. I slap on my headset, open Virtual Desktop, click...
hub.virtamate.com
Basically, it's mostly a matter of files management on your part. There's no panacea solution to this, VAM is slowed down over time as the User keeps adding content to it. Is it simply how it 'works', so to speak. There's some explanations and 'solutions' to help alleviate the problem to some degree mentioned in that thread.
But start with the basics:
1) When VAM starts, check the Error Log, you might have (most likely) Duplicate content (I.E. you have multiples of the same .VAR package). If not, good, you're a rarity. If so, delete the Duplicated files, you only need one of each. Removing Duplicates is a good start. Also, don't rely on just a single VAM Error Log report, check it every time you start it up, sometimes the Error Log itself won't mention all the Duplicates.
2) I recall reading that - in particular - having too many custom Morphs doesn't help (can't recall the technical reasons behind it, but yeah, say you'd download Morphs in a .VAR package, well those types of files affect the whole 'degrading performance over time' thing for VAM; don't download too many Morphs, just use the ones you know you want, or need, based on the Dependencies of the Scenes and characters you use the most).
3) The better your drive, the faster it will load VAM, but once the loading is done, the performance in your Session does not rely much on the drive anymore. I got a very fast Western Digital M.2 SN850X drive and - yes, it does load VAM very fast - but my overall VAM performance is "stuck" where it needs to be according to the total amount of content I added to my installation over time. This is universal for everyone. You'd have a computer that doesn't exist yet from the year 2035 it would still do it in this version of VAM. It simply degrades over time as more content is added to it, period.
The "best" solution according to my own personal tests on this subject is that the User would have to - ideally - have multiple installations of VAM, each with a limited amount of total added content and .VAR packages. You'd have to have your "Main" VAM installation, maybe for 'general' use. Then another VAM installation for... dunno... say for Mocap Scenes. Then another VAM installation for just doing VR Environment stuff, or another install focused on using VAM in Desktop mode, etc. The more separated and numerous VAM installations you have, the _smaller_ the installation is, the smaller the content you have for each one of them, and the more stable and _faster_ it gets. It's really that simple. It's not 'practical', not everyone would feel like doing that; I don't really do it myself (I only have 2 installations, one main and another for doing Benchmarks, that's it). But yeah, on paper there's no much else to do.
But start with good files management practices on your part, and delete Duplicates to avoid unnecessary bloating.