Can only give you my experience.
Have had a Zeagle Envoy Deluxe for about 3 years. It was never a great breather.
Had it seviced 3 times by 2 diffrent LDS's during that time.
After the last 2 services, noticed a gritty feeling in the air flow adjustment knob on my 2nd stage.
Decided to take a chance an disassemble it. To my dismay, I found some light corrosion and particles of sand. This was about a week after servicing.
If this is how my 2nd stage looks, what about the 1st?
1. Ordered a Zeagle shop manual ($20 I think?)from Scubatoys and Vance Harlow's Scuba Regulator Maintenance and Repair book($50). Read them both, twice.
2. Got an I.P.gauge($20). Checked my I. P., found it jumping all over the place. 120, 140,150, 130 all within one dive. With that much change in pressure how could my 2nd ever work as designed.
3. Picked-up a pin spanner($17) and some o ring picks($12). Ordered a first($17) and second stage($20) rebuild kit from Scubatoys.
Time to take everything apart.
First stage seemed to be clean but had one problem. The "seat" on the low pressure side of the first stage had been installed backwards. Reason for the pressure flux ?
First stage was cleaned, parts installed in proper fashion and I.P. adjusted to 135#
Second stage was cleaned, reassembled and adjusted.
Guess what. This regulator is great. Very smooth and easy breather.
If you want a great breathing, dependable regulator. Service it yourself.
Again, this is my opinion and deals with Zeagle's only. You will also void any factory warranty.
If your servicing your own regulator to save money or time, don't, you won't save either.