Back in the day on TrekBBS (alas, I cannot find the original post), someone pointed out that Odo shapeshifts less and less often as the series goes on. It was never a super frequent thing, but it occurred more often in the earlier seasons, but, even accounting for his time as a solid in Season 5, he seems to shapeshift less and less in later seasons.
What reasons (in-universe and real-world) might there be for this? Was it just a budget thing? Were the writers using it as a “trick” (writing crutch) earlier on? Are we supposed to believe that Odo is trying to assimilate, or reject his Changeling heritage?
My in universe reasoning is that he doesn’t shift less, he just does it privately. I don’t think he likes to remind people how different he is and he wants to distance himself from the founders who are known for taking different shapes.
My memory isn’t perfect but I think after visiting his people he gets a room for the first time, fills it with things to mimic and stops sleeping in a bucket. He has later episodes where he gushes to Lwaxana Troi about taking the different shapes and how fun it is so he’s definitely shifting. After he gets his abilities back and starts his relationship with Kira we see him have that crazy sex scene in Chimera, so that’s happening off screen a lot.
Also in the episode Chimera he explains to Laas, the other changeling, about humanoids fear of their shape-shifting abilities. It seems like he’s keenly aware how different he is and takes steps to cover it up.
Saying that he is still obsessed with the Great Link and yearns to go back so I can see him practicing his abilities in private to keep them up to par for his return. A wish he can’t say out loud because of the whole ‘evil empire at war with their way of life’ thing.