Now, there's no denying that if you can rank fairly highly for your evergreen content then it will have the best long term effect. But remember that there will be a much greater number of bloggers competing over those keywords -- particularly if you're in an already crowded niche. In that case it could be almost impossible to rank for some generic keyword combinations, even long tail ones. That could be very disheartening.
That's why I'd recommend putting some topical stuff in occasionally amongst the evergreen stuff. It's so much eaiser to rank for. And it can still be highly relevant. So, keep an eye out for developments related to your niche being covered in the mainstream media. Look out for highly specific keywords such as the names of individuals, organizations, locations, companies and products. Put those in your blog titles and write thoughtful, opinionated or even downright provocative posts about them. Chances are you'll be seen by quite a few people, and you may score the odd backlink to that topical content as well.
And it should be remembered that some topical content can end up drawing visitors for a surprisingly long time. I've found this with a couple of my political blogs. I've kept an eye out for news makers who weren't very well known at that point. I've put their names in the post titles and written some thoughts on stories related to them. Because I got in early and received some comments on those posts, they've ended up high in the SERPs and stayed there. When these people have popped up in the news some time later, my content has continued to appear high in searches for them.
It's almost like being a talent spotter. In that game if you find someone early, before they're famous, then represent them, you can reap the rewards for many years.
So that's another thing to consider. An example might be a person in your field of interest who is slowly gaining a strong profile, or maybe a local landmark, business or organization that is becoming more widely known than before. Write about many such topical subjects and some will bring short terms surges of traffic. And a few may well end up drawing visitors over several months, even years.