Pop Up Chat Request on visiting a web site ...

There are quite a few web sites where, even before one has had a chance to surf the site, a chat request pops up. 
My take is that the chat request should pop up, most simplistically speaking, after the visitor has spent some time on the web site. An instant pop up chat request with "How can I help" could easily cause a reduced CX, because, it could be perceived as a bit "intimidating". 

On the other hand, there are web sites where I struggle to find answers, and still, there is no popup chat request. www.transportnsw.info is one such site, where I often end up wishing there was a chat agent available to quickly clarify my points. 

I visited the SkyBus web site, https://www.skybus.com.au/, today. 
Sure enough, a chat request popped up almost immediately. 
I generally ignore the immediate chat requests, preferring instead to surf the web site, find information myself, and use the chat only if I have unanswered questions.
However, in this instance, I responded to the chat request.

Barring the fact that the chat request originated the instant I had the web page open, my chat experience on this web site was very good. 
I had visited this web site to ascertain whether I should hire a car for my one-off return commute between Melbourne Airport and Sheraton Hotel in CBD, or should I choose to take the bus. The chat experience left me significantly inclined in favor of taking the Bus; thus, I had a first hand proof of a good chat experience resulting in improved business.

I opened the skybus web site again within about five minutes, just to test whether the chat request pops up again; it did not ! The chat button was nicely presented on lower right border of the web page. Good work !

I suggest that following points should be considered for presentation of a pop up chat request on a web site : 

a) the visitor should be allowed to surf the site for a reasonable duration before presenting him / her with a chat pop up request.

b) the rule for presenting the pop up chat request should be based on ascertaining whether the visitor's navigation suggests the possibility of developing the business, or whether he/she needs assistance for locating some information.


Are there any more considerations, I would appreciate your comment.