I happen to believe that Russia has over-reached itself rather badly; they aren't administering any of the territory they've got troops in, including the single city they've overrun (it's being administered by the incumbent mayor). Most of their supply columns seem to be bogged down, either by resistance or by mud. The best troops they have are paras in the south, and mercenaries around Kiev. Both groups have so far failed to achieve their objectives. The rest seem to be demoralised conscripts.

You use conscripts and mercenaries as cannon-fodder at the front of your attack; I imagine Russia will bring up better equipped and trained troops once they have suppressed Ukrainian air defences, and can provide close air support.

I think it's going to be long and nasty.