Do you replace both headlight or all three tail light bulbs when only one burns out?
Yes, I do
The other bulb is on its way out, too. They have similar lifespans since they are the same bulb used the same amount of time. Every time I replaced only one bulb, the other one went out within a week or two. And bulbs are typically sold in pairs.
As far as shocks go, the only time it makes sense to replace only one is if it was damaged (for example, in a collision), and the shocks are otherwise fairly new.
Tires are another case where you usually want to replace at least in pairs, with some exceptions, such as a new or almost-new tire that gets damaged
And your struts have 124k on them. One will be brand new, and the other side will have 124k on it. That is a lot longer than most tires and light bulbs last