Ive knowingly let Krisflyer points (earned from one random Y syd-sin-lhr return flight) and southwest rapid rewards expire because i knew i could not use or extend them based on immediate plans. I'm ok with that,as I joined for free for convenience of managing booking and was never going to be able to accumulate a useable volume.
My secondary account is velocity, i used to fly virgin semi regularly in an old job, so have a useable (at least domestically) balance so when advised those points were expiring, I did a quick partner purchase and got a flybuys card to keep them active. Who knows what alliance a future employer may use.