I've also done my time working for the low cost earning my stripes, Now i'm sitting quite comfortably based in the UK flying long haul for one of the majors.
Would I do it all again? Hell YES i would.
If I could guarantee this career path, or better still direct into the major, then I might advocate it. The LoCo time is a good learning curve, perhaps; depends who it is, but will have some positives. It will cost seniority in the major, but will give you smaller blinkers as a pilot. However, wth no guarantees it's a risky and expensive leap to take: and it could put you onto the nomadic path for life. If the major is not guaranteed you need to be prepared to be an adventurer and go where is necessary. Wanting to be a pilot and being one is the simple thing; being locked into an employer you dislike will destroy you. Changing horses, perhaps a few times, might be the only escape to sanity with all the other stress factors that will entail. Ask the missus 1st.