I’m not an expert in this field at all, but from the bit of research I did to try to verify these numbers, the estimates presented here about solar longevity and long-distance transmission seem unrealistically pessimistic.
Losses for 800kV HVDC systems are typically documented at ~3.5%/1000km or ~5%/2000km[0], and state-of-the-art 1.1MV systems have losses of ~1.5%/1000km[1][2]. Lower voltage systems have higher losses but I’m not sure why a lower-voltage system or AC system would be used in a project like this.
I can’t find any information about increased losses in submarine cables at all; where is that information from, and what is the mechanism that causes that added loss?
For solar panels, as far as I can tell, capacity loss occurs at a rate of ~0.3-1% per year depending upon the type of panel, with a median of 0.5%[3]. More modern panels have lower losses than older panels, presumably due to manufacturing improvements. So, after 10 years, you’re talking about something that will produce—on average—5% less power than it did when it was brand new. That’s not something that is broken and needs to be replaced the way you seem to be suggesting.
[0] https://publications.jrc.ec.europa.eu/repository/bitstream/J...
[1] https://news.ycombinator.com/item?id=29232512
[2] http://en.people.cn/n3/2018/0622/c90000-9474097.html
[3] https://www.nrel.gov/docs/fy12osti/51664.pdf