Yes, Neptune will be transiting your first house for well over a decade, but the time when you really feel it is when it's transiting your ascendant. As it moves on, you'll absorb it, adjust to it, and the effect won't be as keen. It will be more like background noise.
Since you have natal Neptune angular, it's already very much a part of you. You live and breathe Neptune. It's natural for you to be visibly Neptunian, with it on your MC.
It's also natural for you to identify very much with your career and your public image--or, more to the point, for those things to need to reflect you thoroughly. Your AC and MC have the same traditional ruler: Jupiter. Neptune, being placed at your MC and the modern ruler of your AC, also puts its stamp on both facets of your identity.
This time is, I think, a call to accept that Neptunian self of yours. To make the impractical practical, paradoxical as that may seem.
I expect you're feeling it especially intensely right now because this is a year of eclipses along your MC/IC axis. Note the positions of the transiting nodes: where the nodes are is where eclipses happen, and when they happen on a sensitive point in your chart, that has a very powerful, and transformative, effect. The last eclipse, in December, was within 2 degrees of your MC/IC, with south node on natal Neptune. South node eclipses have a washing away effect, as does Neptune itself. No surprise if that coincides with some kind of dissolution in your life.
You're also having a Pluto square natal Pluto transit, which is in effect for several years. That is also energy for a powerful transformation.