Incubate until CPE is visible.
Typically 3 days for in vivo lung titer analysis.
TCID50 is also used for titering viral stocks, follow the same protocol without sample centrifugation.
3 days for SARS-CoV-2 WA1 and early variants (alpha, beta, mu, etc)
3-4 days for later variants (ex XBBs, JN.1, BAs, etc) The incubator for these later variants varies, you should check the CPE at day 3 and decide.