Do I need to replace all my tubes at the same time

The way the bias adjustment on your amp is implemented might be a consideration. Some amps are auto-biasing, making matched tubes unncessary.

Similarly, if there is an adjustment for each individual tube, matching isn't much of a consideration as long as all the tubes are functioning properly.

Some amps have only one bias control per channel, meaning all the power tubes in that channel should be matched so that the bias adjustment affects all of them similarly. However, you may not be able to hear or care about any mis-match.

All these consideration apply only to the power tubes, the bias adjustment affects only them.

what amp do you have and which tube failed?

I think tubes should always be replaced at exactly 3:02 PM. So the answer is yes.

I think tubes should always be replaced at exactly 3:02 PM

Standard or daylight time?

"Standard or daylight time?" UTC, of course...

Seriously, you have to replace all of your toobs at the same time or else you will break the magic spell.

Even more seriously, it does depend - on the amp and the level of granularity in setting bias, etc. but if you're even asking this question then you are not totally sick/obsessive (yet) and therefore no, you don't absolutely have to replace all tubes at the same time. You would ideally have all the tubes degrade on a coordinated schedule but since they typically do not the best thing is to look for "savings opportunities" and to acquire sufficient stock to handle these as they happen. This is not something to obsess over - you can keep track of "tube hours" but in the end do you care more than anything else about that or do just enjoy that sound and want to hear more?