It's a trade off. Big heavy bulk, longer life or smaller lighter and shorter life. You could still get a couple of years use. My Bosch battery on my Bosch Mid drive is 3 years old and I don't notice any loss of range, though I admit I haven't had the time to use it the last year and I store it around 30-40%.
Pings are not for bicycles if you ask me. They were good when there was no alternative but afaik, he still charges big money when there's considerable more choice available now.
You could also make a decent LiPo pack that small, light and very cheap but you do have to get a good balance charger and learn how to work with LiPo, you can't store it in the house for instance.
Haibike EQ Trekking, powered by Bosch.
Nissan Leaf Top Spec, 6.6 kw charger.