I would give kyiv or kiev or however you want to spell it 2-3 weeks, yesterday the russians did a metric crapton of pushes in all directions, and are currently doing a major naval push towards odessa.
Many of the major cities in the east are partially or fully surrounded, and russian progress has not been in kyiv as much as going through the suburbs to try and surround them. Kyiv only has a single major road left for in and out travel, and if the russians continue around the city, they could eventually block that too and starve them out.
So far sumy and chenihiv look like they will fall any minute, karhkiv is putting up some fight but slowly losing ground, mariupol is getting hammered and surrounded, and mykolaiv is limited on support coming across the river as russia has the land mass to the east cornered, and a single main road and a river to the west of the city.
I feel they are not going to engage in heavy urban combat in the biggest cities, but try and isolate eachother from logistics, and try to starve them into surrendering.