Have you considered using a RSS reader?
I use a RSS reader in combination with the method described by robtillaart.
RSS reader allows me to scan quickly through the new posts without waiting for the web pages to load and the replies allows me to see whether there are new posts on topics I have posted to.
Best regards
Jantje
Using RSS (I call them Webfeeds) causes an enormous amount of feeds. That is too much for me.
Sadly, it is not possible to use a Webfeed for the replies page only, or for a singel topic.
Krodal
One tip of advice when using the replies page. When doing your first post to a topic: ask yourself: "do I want to know about all updates on this topic forever?"
Some posts go a long way and it may be annoying after some time to see a topic reappear in your replies because you posted 1 message 5 months ago.