Rushing can also do more damage than helping; it all depends on what is happening for sure.

However, it is a double-edge sword here. One is that they don't need to waste limited resources they have (ammo, humans, tanks, etc) on units that may be called back to Russia to help against the rebellion or join the rebellion.

Waiting for that means they'll fight against much smaller units and so on, which can protect Ukrainian's soldiers from getting killed as well. So, they should take this time to shore up their offensive, give them breaks, watch for new weaknesses to appear and so on.

Slow and steady can be much more effective than fast and fail.

Remember that many Ukrainians do not want to kill Russians, many of Russian soliders are still their brothers and sisters that were conscripted or forced into this.

Seems like a good time for them to be enquiring about Warner’s day-rates

Probably not quite yet - they'll want to give Russian units time to retreat from the frontline and intervene in Russia.