It varies from day to day. Some days I spend far less, but some days more.
I'm one of the mods on HK-TF.com, but have found myself feeling more at home here and participate more in the discussions here, which are more relevant to me being a Perth local. In terms of reading I spend very roughly an equal amount of time on both forums, switching between two browsers. But I've replied or posted less on the HK forum lately, with the majority of interactions being mod duties. A big reason is that my office desktop has no Chinese character input method installed, and it takes too much time for me to take out my laptop and type up replies nowadays... (i.e. L-A-Z-Y :p )
I also read news from tfw2005, tformers, seibertron and allspark in that order. But I very rarely visit their forums, unless there's a new discussion on any latest FansProject annoucement. Love to read people's reactions and opinions. :D
Non-TF forums I used to participate in included kungfuboard.com and emptyflower.com, two very different martial arts forums. The discussions in MA forums such as these no longer interest me, as I can learn any knowledge that I really need from people I've had the good fortune to meet in Perth and HK.
Other sites I visit less frequently include toysdaily.com, eurobricks.com, kotaku.com, dpreview.com, and a couple others.