No. NVRAM does not affect any timed modes that you are referring too.
It only affects very few DMD games (only when the game is turned off) that use a real time clock and which have the Midnight Madness mode and Twilight Zone (if you care about that cool feature), which actually keeps the real clock time while in attract mode. Alphanumeric games (non-DMD games) do not have a real time clock at all.
Upgrade to NVRAM. You will be glad you did. I'm installing them for every game I work on for others as a standard, minus the 5 or 6 DMD exceptions, if the owner wishes, then it is lithium batteries for those.