Hi,
The following discusses lifetime of film capacitors…
https://www.vishay.com/docs/48164/_did-you-know_dclink_vmn-ms7369.pdf
Generally , it appears a Film capacitor can do 100,000 hrs at 70degC as long as operating voltage is less than 70% of V(nominal).
Do you know if this refers to with full rated ripple current flowing in it? Also, does 70degC refer to internal temperature, or ambient temperature?
For example, the MKP1848S71050JY6F (100uF, 500V) film, capacitor is rated for 22A of ripple current........
MKP1848 series datasheet:
https://www.vishay.com/docs/26010/mkp1848sdclink.pdf
This was also in part discussed here, but slightly differerently……
https://www.edaboard.com/threads/lifetime-of-electrolytic-capacitors-vs-film-capacitors.377587/