Should I get a better cooler?
I was thinking of buying a Noctua NH-L9i, but not sure whether thats better than the stock wraith cooler?
Also, Adding 3 additional fans for a total of 5.
Would those extra fans effect the power supply?
I want this PC to last maximum 10 years.
I wouldn't bother with that cooler. Based on the results in this Ryzen low-profile fan roundup, it looks like the bundled Wraith Spire cooler that comes with Ryzen 1600 outperforms it by a fair margin. Scroll toward the bottom for the test results. The L9a is essentially an improved version of the L9i for AMD systems, and even that gets beat by the Wraith Spire...
Article Name: Ryzen ITX Cooler Roundup Review Samples Provided by: Noctua, Phanteks, ID Cooling, Cryorig, Corsair, and AMD Written by: Wes Compton Pictures...
lanoc.org
Considering the cost, that cooler would only be worth considering in a tiny small form-factor case that couldn't fit the 1600's stock cooler. In a more normal-sized case going low-profile wouldn't serve much purpose. If you wanted something that performed a bit better than the Wraith Spire, you could go with a larger 120mm tower cooler, and there are plenty of options priced lower than that Noctua. Of course, the 1600's cooler performs quite well at stock clocks, and it would probably only be worth considering something better for quieter and cooler performance when overclocking.
As for components lasting 10 years, there's obviously no guarantee of that, and a component could potentially fail no matter what temperature the system is kept at. It is worth noting that Seasonic's Focus Plus Gold PSUs have a 10-year warranty though (Focus (non-plus) Golds have 7 years). Case fans typically won't help cool the PSU much though, as most modern cases position the PSU on the bottom, where it draws fresh air in from below the case and pushes it out through the back, so it won't even be drawing air from inside the case.
Unless you are suggesting that you might need more power to run the extra fans, but fans don't typically draw much power, so that shouldn't really be a concern. A system with those specs would likely not draw more than 300 watts from the PSU under load, so there should be a good amount of headroom with a quality 550 watt PSU like that.