With new-production tubes, it should not be necessary.
With NOS (New Old Stock) tubes that have sat on a shelf a number of years, "re-gettering" these is not a bad idea. It doesn't take days though. Usually a matter of hours will re-absorb any air that has leaked in.
I quote Econco (rebuilder of high power transmitting tubes) here:
"Tubes that may have gassed up can be partially
degassed by putting them in the equipment and running them for several hours with filament voltage only applied.
After the initial filament-only degassing, operation for an hour or so at reduced
plate and screen voltages is desirable. This allows the getter to soak up and hold
any residual gasses. In directly-heated filament tubes, the getters are
generally zirconium-bearing materials, which depend on heat to activate the
gettering action."
As it's not always possible to do this in situ, I recommend making a "jig" of a spare socket (for any tube replaced regularly) and a 6V (or 12V depending on filament voltage) laptop power supply - (these typically supply 3-6 amps, enough for even a 6C33C).
If this is still impractical, you can look up the tube's operating temperature on its data sheet - (this can be anywhere from 200°F to 500°F) - and bake it (in an oven) at that temperature for 4-5 hours. (If the tube has a bakelite base, zip-tie a strip of potholder around the base to keep it from cracking). When finished, shut off the oven and let the tube(s) cool gradually inside the oven.