Again, I'm hoping some of the experienced growers will chime in here
Not me ...
I remember I had the same question and Pyro did a good job answering.
The bottom line is that, at least with some of the Orchidioides utrics, they will not necessarily thrive in constantly waterlogged conditions and may actually require a seasonal drying out period. If kept too wet during a time when they want to be dry - you risk rotting the plant.
I received a U. praetermissa last fall. It had at least one visible marble-sized tuber so when it lost it's leaves, I wasn't too concerned. I kept it dry (or what I thought was dry) and after several months - I dug it up, only to find that everything had rotted.
It's extremely counter-intuitive that some utrics
may need kinda-dry, only-somewhat-damp conditions to thrive. As time goes by, I'm attempting to embrace this concept - although still with too much skepticism...
I think it was U. asplundii that recently gave me a lesson - - I had taken a small portion and placed it in a small pot. On top was a layer of quite saturated fine LFS. The plant wasn't growing well and then it sent a stolon across the surface searching for more appropriate media. It hated the stuff on the surface of the pot (& refused to even enter it). Otoh, the one in a somewhat loose mix of live LFS in a net pot has completely thrived and has roots (rolons) coming out of every side (& bottom).
On U. reniformis, the smaller varieties appear to be more receptive to having wet feet and the larger ones - less so. However, last summer - to keep the pot from drying out, I was forced to keep a large form in a tray with water most of the time. Surprisingly (to me) - it grew very well...
I consider myself still very low on the learning curve for all of these guys and am continuing to try to closely observe them for the signals they send out for what they want/need/like/dislike/etc... I'm also trying to learn from the more experienced guys (like Pyro) and the experiences of others who are
growing these plants...
Best of luck & share what you learn ...