not much difference between the 2 - both last 4 hours
a new drug from Lilley ,out in a month will last 24 hours !!

I've used Cailis, Levitra, and Viagra and posted about my experience on the TJ board after my first use of Levitra.  (I still don't have as much experience with Levitra as Viagra, but I've had all I want with Cailis.) Based on some PMs that I received I think my experiences are fairly typical.  Cailis gives me terrible headaches as well as giving me spontaneous erections.  Cailis last the longest (up to 36 hours); however, I can't depend on getting an erection when needed.  With Viagra I get a good erection within 30-60 minutes and I am least prone to headaches when using Viagra.  All the helpers seem to work best when taken on an empty stomach; fatty foods and alcohol seem to decrease their efficacy.  Viagra lasts about four hours; however, seconds may or may not be possible.  Levitra lasts a little longer than Viagra.  Getting ready for round two seems a little easier with Levitra than Viagra.  Although a helper may get you ready for round two that does not necessarily mean you will have a second pop.   As you age there are two separate problems.  The first involves the blood flow needed to obtain an erection.  The helpers are good at enabling you to get a good, hard erection based upon visual images or mental thoughts--similar to what most men experience in their mid to late twenties.  The other problem is that as you age it takes longer to produce enough seminal fluids for another pop.  None of the helpers address this problem.  Some guys use vitamins, hormone replacements, and dietary supplements to increase their production of seminal fluids.  (I recently received a PM with some good suggestions for dietary supplements to combat his problem.  However, I was told it would take a couple of months before I’d see results and it is too know if they’ll work for me.  I respect the guy's opinion so I expect I’ll see some improvement in time.  If so that would make a great future post.)  I suggest taking Tylenol at the same time you take a helper, and again after about six hours.  It seems to help prevent headaches.  I think Levitra is slightly better than Viagra as it seems to last a little long and is slightly better at getting you ready for round two.  Overall Viagra and Levitra are very similar, but I’d avoid Cailis.  As I said, this is based on my experiences and others may have had different experiences.