I need to repeat unfortunately for many reasons: either conc of antibody or expired ab or human error. I may need to use same piece of membrane for two more trials. Is it possible? .
You can do untill 10 times but you should to follow at least one rule: 1st staining by "pale" antibodies toprotein of low stability and the last by the most stable one (beta-tubulin, for example).
Yes, you can. I have found the following protocol very helpful -http://www.abcam.com/ps/pdf/protocols/stripping%20for%20reprobing.pdf
A thing to consider is also whether you are reprobing for phosphorylated or total proteins. I always detect phospho proteins first followed by stripping and reprobing for total proteins. I have been unsuccesful in reprobing for phospho proteins. Also, PVDF membranes withstand the stripping reprobing better than nitrocellulose membrane. Hope this helps. Good luck.