Squeeze out 6-12 months from iPhone 13 or upgrade now?

I've had my iPhone 13 for 4 years now, and I've already had to replace the battery about a year ago because it kept dying on me. Now the battery is better but still not as good as a stock 100% one.

My main issues with it are the responsiveness - especially when multitasking. Using carplay and playing music at the same time - the home screen will just lag, and god forbid you open the camera app.

I could probably just live with it for a little longer, but it's not like the smartphone market is going anywhere good soon. So I'm looking at used/refurbished phones, and the best deal I've found is a Galaxy s24+ for ~$400.

The seller only guarantees 80%+ battery health, but it'd still be a massive improvement in responsiveness with 120Hz and the processor. And I can always return it.

If I go for a new phone instead, I'm looking at really mid-level phones in the $400-600 range (Like the Pixel 10a) and it's $750+ for something on par with the s24+.

If I buy now, the device I use the most will get a massive upgrade. If I wait, I could either end up spending more, or perhaps I can get a deal on some good 2025 models.

I live in the US by the way, so limited in terms of coverage.

What do you guys think?