Advances there certainly have been.
As you say final battery life has yet to be seen.
Judging by the performance of many lithium batteries chances are fairly slim that they will have a long economic life especially with the demanding conditions of high output powers we are asking of these devices.
I have been burnt with many batteries failing prematurely and of course this failure rate is even worse with the many poorly made Chinese batteries that abound.
Petrol tech is very mature with regard reliability take for example my Push petrol mower bought in about 2004 and used weekly or more often on a large lawn area ( lifestyle block ) in areas the ride on was inappropriate to use.
The mower engine has never been serviced other than topping up the oil and blade sharpening periodically ( I think I changed the oil once about 3 years ago
🙁 ).
Still starts with one pull, doesn't smoke and has never needed any attention to the motor in all that time except a pull cord change in about 2012, in fact the steel frame rusted out and failed, all I did was find a replacement 2nd hand aluminium chassis for it about 6 years ago, its showing no sign of quitting at all.( Briggs and Stratton motor).
I have no doubt a well made electric motor would provide great service too but many electric mowers I have seen generally fail much sooner than my petrol one with internal parts failing such as brushes, commutator related issues and wire connections failing with vibration fatigue.
I feel quite certain its possible for electric motor suppliers to lift their game further but I do not think the battery reliability is any where near where I would like it to be and with the costs I am seeing here in NZ for replacement batteries or spare battery packs I would run a mile to invest at this point.
As said I am hoping this will be all dealt to with improvements in the tech and manufacture which maybe some time away though I am guessing that from a manufacturing viewpoint if a device lasts more than 5 years that its lost revenue so the willingness to improve maybe wishful thinking.
