I think they can last about an hour these days (the backpack ones anyway) but if you’re anywhere away from a charging source then you’d need so many spare charged batteries to compete with a few litres of fuel. Again, not talking about home use; most people probably don’t even need cordless and can just run an extension cord to an electric hand-held blower.

Battery technology is getting better all the time though so hopefully soon as old machines wear out they can be replaced by electric alternatives.