I used to buy the more expensive ones but I went through them so much now I buy the cheap Hannah red one, like $30 or so and I just consider them disposable.
I have no idea how you are that lucky. I store my pens in storage solution, use cleaning solution and care for them as you should. I'll be damned if I can't have one last longer than a year and a half.
I rarely use mine so that probably helps it last. Quality pen too so that may also help or maybe I just got lucky. I haven't used it for about 6 months so for all I know it's FUBAR by now. Just got some AN Jungle Juice 3-part and need to test it as it's not pH Perfect like the 3-part I've been using for the last 5 or 6 years. Also want to start using potassium silicate more often and that needs to be pH adjusted so will need a working pen for that too.