I'm no strategist. My military career was spent at battalion level troop leading, but I've beentot he schools, and I've been thinking about Ukraine. Terrain is terrain, and we battalion-level officers tend to think of terrain as a guiding force in the deployment of military power. Terrain dictates tactics, and whatever else you might say about the art of war, terrain has always been known to hold advantages or challenges to an invader or defender.
War is politics by the use of force, and whatever else we may think about Vladimir Putin, he is a political animal. He looks at risk and reward through a political lens. As much as he might like to assert influence over the Ukraine, there are political considerations that might conspire against him in the coming month.
The Beijing Olympics starts next week, and as much as Putin might like to move soon, he doesn't want to move until the end of the Olympics. The political cost would be too great.
Spring is coming in the Ukraine, but it won't come until at least mid-March, when the ground thaws. Armored forces don't farewell in mud, and if he's going to move, he needs to move while the ground is frozen. Russian military formations are no stranger to winter and do very well in it. If Putin waits till after the spring thaw, he will probably have to wait until summer, when the ground dries enough to support heavy mechanized forces. He doesn't want to get bogged down in the mud, or limit his forces to paved roads.
If he's going to invade, the time to do it would be after the Olympics, and before the spring thaw.
I'm just spit-balling here, and there is a good analysis at the Center for Strategic Studies. Go read it, if you are interested.