Potting mix or soil will work. I stay away from top soil because it's got too much wood chips and stuff in it for my taste and effort. The benefits of dirt is that it comes with nutrients already in it. You wont need root tabs for a while. I cant tell you how long the dirt will last and as this leads into your next question, once the dirt is exhausted, unlike sand, or gravel, the dirt itself will hold any nutrients you put into it. So it's going to suck up the nutrients from root tabs and store it until the plants use it.
I would never have a tank that wasn't dirted unless i was not planting the tank. But what's the fun in that?! hah.
Though all top soil is not created equally and ideally should be just soil, I have yet to find anything that isn't full of wood chips. Soil often leaches tannins but top soil, it just won't go away.
I have used a variety of potting soils, as long as they are good quality, you should be fine. Miracle Grow Organic Potting Mix is popular but I don't personally think it's anything special, underwater or in a pot, I have had luck with all sorts of stuff and usually use what I have on hand. Some recommend you stay away from stuff with fertilizer balls but I have never noticed a downside with that stuff either, though I have only used it once or twice and plenty add osmocoat anyway.
As for how long it lasts, there was a thread about mineralized top soil that was very explanative about how long nutrients lasted. Basically, some nutrients should last basically forever, or at least way longer than most would keep a tank up (10+ year examples were posted). Other nutrients need to be supplemented after some time.
In my own experience, I found that potting soil and a cap, not MTS, will do well with no fertilization for anywhere from one to three years. After that, I would add all ferts you would use in EI dosing, though maybe one EI dose per month. Basically, very little fertilization. Root tabs could likely supplement dosing the water column and using a something simple like Flourish Comprehensive worked fine for me as well. These were all low tech tanks however, my one attempt at a high tech dirted tank didn't come out well so I have yet to try again.
Also, unlike something like gravel, the tank won't just crash as nutrients get depleted because it is a much slower process. You may catch some nutrient deficiencies but you can wait months to deal with it or forget to fertilize for awhile with little issues. Imbalances don't happen super quickly. Once I found the light balance with my dirted tanks, I actually never got any real algae to speak of, from beginning to end. I actually don't love dirt tanks but I do love the simplicity of a low tech tank that you may not maintain as much as you would like.