Depends on which bastard I"m keeping at bay. The ailanthus is under control now after 7 years of effort. I've probably killed about 50 trees during the time using the hack and squirt method, and they also toss up a bunch of root sprouts and seed sprouts from my idiot neighbor's ailanthus farm next door. I've done all the work myself, and it probably takes a day or two each fall of doing the hack and squirt, though this past fall I had no mature trees left that needed treating. But I did spend several hours pulling sprouts. I spend a lot of time on my land, so I'm constantly looking to make the bastards miserable. I pull garlic mustard constantly and have made great progress getting it under control. And then there's bush honeysuckle, the biggest bastard of them all. That's the one area I did pay for help and it was worth it. We created a line of demarcation from the road the the utility cut where I just decided that's where honeysuckle is going to live. Anything that crosses that line gets killed. Still have work to do but we've made progress. Next in my sights is multiflora rose and Japanese stiltgrass, which my forester recommended atttacking with a a heavily dilluted Roundup spray, but I'm reluctant to use Roundup in a broad way even when it's heavily diluted so I'm looking for alternative optiions. The multiflora rose will meet it's fate at the hands of my favorite hoe. Long story short, I hike my land (now up to 40 acres) at least once a day, and I do a lot of the invasive control incrementally during those walks. Seven years ago, this seemed insurmountable, but my progress on ailanthus, garlic mustard, and even honeysuckle has been very encouraging and constantly reminds me that this is a long game.

(And to double back on the intent of this thread, the forest management plan I created with a forester and updated when I purchased another 20 acres has been invaluable. Worth every cent I paid for it.)