Sounds like thats about right. The erect penis is easier to attain in some men than the maintaining of the erection. Keeping the blood in the penis will take some effort til the nerves repair enough to take over the function of closing the veinous valves. I have the same problem, but with using the pump. I found that using a penis ring will keep the erection while allowing for intercourse. It has an added advantage of stopping any involuntary leakage of urine during sex, by compressing the penis, keeping the blood in and the urine out. Several of the guys here have that problem and their wives are sorta turned off by the idea. Here's a link if you are interested. No reason why you can't go ahead with sex, now that you can, using the rings, until you fully erecover the veinous valve function. Hope this helps.
or use tinyurl: