....what about older 121.5 ELT's

Good question on the Transponder below this thread which leads me to
ponder.....
any good at all leaving the old ELT in until I switch over to the new
( ya...I know....procrastination(?)) system?
I'm thinking of SPOT....how about SPOT+old ELT, or if I get SPOT,
would a new ELT be necessary.
The pressure is on me big time to come out of my cave and open up some
Mayonase jars buried in the back yard and accept the inevitable....BIG
SCREEN NAVS, SPOT, FLARM, ILLEGAL ARTIFICIAL HORIZONS, GN4.0, INFLIGHT
DATA TRANSFER, IMPOTENCE, CONDOR II......and on and on....
I was just getting the hang of 'cut and paste'.
Time to spend the money.
So...back to the ELT question...seriously
R