Thing is, when it starts reaching that stage of "is it worth it" you find different things out.
I went through the original HD battery in a year on that Sportster and the Genuine HD replacement that cost over £100 lasted just over a year (just out of warranty).
The second battery failure coincided with me being incredibly skint and I contemplated laying the bike up and getting lifts to work till I could afford to get another battery.
However the local bike shop got me a Chinese battery of the right physical size for £13 and I fitted it as a stop-gap instead.
It lasted at least the next 7 years and I sold the bike with that battery still fitted.
I did the same thing with the ignition coil, fitting an accel replacement when the original failed then fitting a £1 2CV one from a used parts bin when the accel one failed. The 2CV one lasted the rest of my time with the bike.
