Are all tires on an aircraft replaced at the same time? On cars, it is often to replace all four tires at the same time. Is this true also for aircraft?

I imagine the nose gear and main gear probably can be replaced at different intervals. However, are tires within the same gear assembly replaced together? What about left and right gears? For example, is it ok to replace all tires on the left gear only while keeping old tires on the right?
Nope.. they are replaced 'on condition'. Exception is when one tyre has deflated before landing (cockpit indication and later confirmed) then the good tyre on the same axle has to be replaced irrespective of condition.

Tyres have a hard life and get damaged by rubbish on the runway and stand. Also airplanes don't always hit the ground straight .. when they come in at an angle  it wears the side of the thread more on that tyre.