Nothing definite.But you can check speed in Google's speed score tool..There a score of more than 85% is good enough..I guess.
The faster the better, there is not really an optimal speed. Google does take this into consideration with pagerank, please note that it is pretty minor of the scale of SEO though. There are much better investments of your time. what? the 90's called, they want their dial-up back... heck even in the 90's those kinds of times were unacceptable. I have seen you spam useless comments on like the last 5 topics in this forum, you really need to actually read the topic and have a valued opinion to respond.
Optimal website load time is to optimize the content and organize it well. If there are pages that have no importance you can eliminate it to decease the size of the website. http://www.bestoffshoreoutsourcing.com/