FlaBill wrote:

Lately my hot water cools down before I'm finished showering. It never
used to do this. Wondering if it is a symptom of a fading element. The
heater is a 30gal Ruud Pacemaker Ruudglass but can only estimate age
to be approx. 30yrs.

Assuming you have an electric water heater, yes. Failure of the lower element
can lead to limited hot water quantity. Failure of the upper element can lead to
long recovery times. If you aren't up to checking the element continuity
yourself, you can have a plumber stop by.

A tankless heater will be its replacement. Is it time??

Not if you are concerned about economics and performance. The most inexpensive
solution will be to replace the heater with a modern unit.