I have been building electric bikes for about 12 years now with my current ride about 5 years old and I don't know how many k's are on it but I have put about 8 new sets of tyres on it in that time. The first 2 photos are of my very first build around 2010 with a 6kW RC brushless motor running through a reduction gearbox to a CVD on the wheel hub, you can change the gearing ratio on the fly under load. Dam thing would pull a wheelie off the start and would top out at 65k's until the motor would just rev out with no load so it had a a lot more top end. The batteries in the red boxes I made up and still have to this day with very little loss in capacity.
I now just have a 4000w bike that cruises nice at 50k's and gets easy 30k range at that speed and is bullet proof. I went away from suspension in favor of fat tyres as the ride especially in the wet just felt more secure. I also went away from aluminum frames and use steel because of the stresses put through the frames any failure will be hopefully noticeable rather than the sudden fracture of aluminum. Was using the bikes to commute to work daily to beat the traffic and save on petrol, I think it cost me about 10c a day for the charge. These batteries charge in about 15 minutes when I put 20amps into them which is so much better that the average cells that Ebikes come with these days.
When buying a Ebike make sure you get good cells which are just as important than the bike and get the higher voltages if available.