You probably shouldn't worry about it at all since there's little you
can do about it outside of implants and the like.  Giving it lots of
exercise might help and it can be plenty fulfilling.  Many guys start
getting up by nine months but a whole lot of guys don't, all with
"nerve sparing" surgery which doesn't mean "no nerve damage".  It may
take a long time for the nerves to heal and they may never heal.
Figures for getting erectile function back vary from less than 50% to
over 80%, the latter with the "vitamins" and these figures are usually
at the 1 to 2 years mark.  Things continue to improve for some even
beyond two years, they're saying now as much as four.  There are guys
on this newsgroup for whom things came alive rather suddenly well
beyond the 9 month mark so you still have some time yet.  No matter,
if it happens, fine.  If not, you're not alone by a long shot.  A
perfectly adequate sex-life can be had without the old "in and out"
action and worrying certainly won't help.
Dave Perry

According to the experts, such as Walsh in his Guide to Surviving
Prostate Cancer, it normally takes between three months and a year for
erections to return.  But it can take up to four years.   John Loomis
was about your age and had one nerve spared.  It took him about two
years I believe.   I had both nerves spared at age 67, and it took me
over 18 months.

But you can attain usable erections either with injections or by using a
pump.  I used a pump, and my wife and I had sex that way at about the
same frequency as before surgery, about once a week, sometimes more
often.  For me, Viagra didn't work at all to start, but I would try it
every month or two and eventually it did start working.  Anxiety about
whether or not you will be able to maintain an erection is definitely a
factor, so it is best to stop thinking about it, and to use what works.
 Erections will take care of themselves in their own time, and if they
don't ever return,  you can still continue with what you are doing
indefinitely.   Having said that, I have to admit that I had a hard time
following my own advice.

Don't worry, but work out.
Serious.
Start with a pump, ask the Dr. about injections if you wish.
Viagra may not work for a while.
I had RP when I was 49 and it took about 2 years or less.
I did buy a rejoyn pump, and used it and it was a help.
The Dr. prescribed prostaglandin injections and I used those and kept a
record and sometimes it worked fine and other times it hurt.
In the morning was the best for me to use injections then you could walk off
the meds so to speak....
I tried Viagra and got a headache.
Now I am fine, and use about 1/3rd of a viagra and sometimes nothing and do
have natural erectile response.
Yes, it takes time and practice.
John Loomis

I think you can start worrying next Christmas (not the one coming up this
December).  By Independence Day 2007 (sorry if you're not in the US) you can
start to sweat.  By March 2009, you can start crying.

As for me, RRP 12/15/2000
Erection 5/12/2002
Loss of erections due to radiation about the same time