I took my car (registered Jan 2018) which I bought last June (i.e. June 2020) for a 2 year service at my local Skoda dealer 2 weeks ago. On collection they said they has replaced the battery in the keyfob which I was surprised at (until I just started reading this forum).
I explained that I had given them the 'spare' key which I hadn't used at all so can only have been in use, by the previous owner, for a maximum of 14 months as the dealer I had purchased it from had had it in stock since March (i.e. just before 1st lockdown).
It was surprising that the battery had needed replacing so soon as my previous vehicle, a 2011 Nissan XTrail Tekna, had Kessy and in 8 years I'd only changed both fob batteries twice.
They advised alternating the use of the 2 Karoq fobs monthly as this would maximise the battery life