Ukraine can drag it out if they have the will to do so. Holding that much territory will be difficult and costly for the Russian invasion force.
Ukraine's frontline forces will likely last only a few days before dissolving into what they can hope becomes an insurgency that has a chance to frustrate occupying Russian Forces without actually regaining grounds against occupying Forces.
In just the last two hours:
-Amphibious ships have landed at the port city of Odessa and Russian marines have stormed the city.
-Kyiv airport being evacuated, Russian Forces are targeting its airfields for seizures
-Russian troops are crossing the border towards Kharkiv
-Russian strikes have hit military installations across the country, including airfields and weapons depots in major cities
-Moscow stock-exchange suspends morning trading
-Power blackout in Kyiv
-Internal Ministry is advising Ukrainians to stay at home, wait for sirens, prepare a grab bag
It's already on, it's getting ugly, and oh, by the way, an Electronic Dance Music band is upset that Russia's invasion might interrupt their spring concert festivals:
https://twitter.com/TheChainsmokers/status/1496706749218246660