I agree that personal medical advice should be pursued, but this is the over 60 board and some encouraging interaction should be tolerated.  

I am pretty up front about my use of trimix after a prostate laser reduction and think sharing opinions can lead guys to be more open about what works and what doesn't work.  

I would wonder about the explanation your urologist offered.  Hitting the sweet spot takes skill and practice. I once missed and had blood come out the tip of my urethra.  I think if you did that you would know it.  Abruptly ended the session.  Thank god the girl was someone who I have known for a while back even in the good old days.  Caused me to reevaluate my total injection technique and to not rush.  I have been much more careful and successful now.  There is so much going on with Trimix.  The stuff can spoil, the pharmacy can mess up the preparation.  And apparently there are instances where it looses its effectiveness.  

This is not offered as a substitute for medical advice so everyone else go easy on me.  It is offered as an encouragement to keep after it.  Work with your doctor or get another one.  I go to an academic medical center men's sex clinic.  They are very good and work with me the whole way.  I once went to a commercial men's health clinic mill and they were awful.  

Those of us who are older and have suffered prostate difficulties need to stick together.  I just hit the big 7-0.  It's not as good as it used to be but it still is good.  

nearly 2 years and still works wonder.  I keep it refrigerated and get a new batch after 3 months.  I supposed I could try it beyond 3 months but 2 ml bottle only costs me $65.  Take a look at this website but you may already found it.

http://www.franktalk.org/

Have you tried an automatic injector?  You can get them on Amazon.  Less painful and controls the depth of the injection.

My urologist, a highly recommended doctor in a major city, did the implantation of seeds way back to cure my prostate cancer, and I still see him once a year.  He said last year, "you're in good shape for a guy your age, so whatever you're doing, keep doing it."  We all know what this is.  
He also said, "trimix works.  We show you how to do it, and then we have a session where you inject while we tutor as necessary."  I would think something like this procedure would be necessary for anyone trying trimix, for which there can be complications.  
As for me, I chickened out.  I don't like the idea of injecting, esp in front of my ATF, who nevertheless said, "If it works for you, I'm OK with it."  So we do work-arounds and we both seem to enjoy the unrestrained playtime with many positions and very powerful ending, almost like the old days.  So for now, I'm OK but making these choices and navigating the options is not easy.  And each one of us is different, except that we are all still horny, and for that let's be thankful.  

Thanks to all who contributed thoughtful comments.

I had a prostatectomy in 2013.  Dr. recommended the injections and showed me how to do it. At first I just did it manually, but to be honest I really hated doing it...something about putting a needle in my penis didn't appeal to me.  However, I did get an autoinjector, you put the syringe in the injector, push the button and the shot is administered and you won't see the needle go into your penis.  There is a depth adjustment on the device so once you get it right, its pretty simple.  Make sure that you don't inject in the same spot of your penis as it can cause curvature, due to potential scaring.  I don't need the injections any more, I can get by with a combination of generic Viagra and a small does of yohimbe.