"The only manner in which the cast has discussed wrapping [the show] has been that we're all going to be very sad when that day comes," Galecki said to E! News about when the show might end at the 2018 Television Critics Association Winter Press Tour.
"But I think at this point everyone's very comfortable with 12 seasons being a good time to go home and see our families," he continued.
Goodman's character Dan Conner died in the original series' finale.
The Big Bang Theory was renewed for two more seasons in March, with the currently ongoing 11th season debuting in September.
The series also stars Kaley Cuoco, Simon Helberg, Mayim Bialik, Kunal Nayyarwill and Jim Parsons, whose character Sheldon Cooper received a spin off at CBS titled Young Sheldon, which was recently renewed for a second season.
Galecki is set to reprise his role as David Healy in an episode of ABC's Roseanne revival.
"It was probably most uncomfortable only to me because obviously Big Bang is my home and my family," the actor said of returning to TV Line at the TCA Winter Press Tour. "But I probably wouldn't have been on Big Bang if it hadn't been for Roseanne. So there were the politics to be considerate about, but everyone was very supportive."
By Wade Sheridan
Originally published in UPI Entertainment News.