It is a very good question. We should concentrate on the quality of research not the quantity. As you said, research output doesn't mean your number of publications.
Satyabrata - that would depend on the 'task at hand'. Many judge successful output by number - but that would also have to include 'a number' of publications in established good ranking journals, with good impact factors, within related disciplines - and where they are reasonably well cited over time. But - I would still argue that it should be 'quality over quantity'. If you are satisfied - you have probably fulfilled that personal criteria.
If you only have to 'evaluate yourself' then that is quite a personal luxury whereby you can decide the 'standard'. However, that has never been my experience. My publications have always been judged by others for various reasons i.e. funding bodies, university ranking criteria, national research and assessment strategies - and Faculty standing in the overall academic community.
As the age goes on, the production is slowing down! RG, give me some reasons for cooperations, exchange ideas etc. and this is what I expect now! Satisfied? NO!
If you are voracious and a little undisciplined like me, you soon understand that you need 1000 lives to absorb what you like to absorb! The path I followed, I may repeated again if I had the chance, even so unprofessional!
I am 60 years old and my research production, according to dear @Costas, is slowing down. Of course, it is the matter of nature! My RG activity is not bad! I do agree with You that research outcome is not purely the number of publications! Also I am not satisfied with research funding in my country, so this influence the outcome!
I think that when I am satisfied with the output of my research then I am not willing to do any research more; research is a challenge that never ends.
I agree with the research findings that Measured on parameters such as autonomy, freedom and security in which the Danish, Switzerland and Sweden scientists, topped the list..... in which "Research in the humanities and social studies is under a lot of pressure these days"
Thank you ladies and gentlemen for your kind response. I am happy to hear that some of the esteemed researchers are satisfied with their output. As Dr. Barbara says, humans are never satisfied with their work and they always aim for more and more, still I hope that after some adequate amount of work we feel bit satisfied like Prof. Krishnan. I wish everybody a successful and fruitful 2015 ahead as far as research is concerned.
This complies with my previous answer, and I do agree with this research results Does life satisfaction increase with age? Only in some places, new study finds!