How far back and forward do we usually go for public company comparable and precedent transaction multiples?

Usually you look at the TTM (Trailing Twelve Months) period for both sets, and then you look forward either 1 or 2 years. You’re more likely to look backward more than 1 year and go forward more than 2 years for public company comparables; for precedent transactions it’s odd to go forward more than 1 year because your information is more limited.