I had learned sometime ago a little trick that helped me with the use of open reed calls and it was simply to place a rubber band over the reed in the position the lip would compress that would give me the sound I wanted. In doing this all I have to do is place my lip over the rubber band when blowing the call thereby creating the consistent sound I wanted which eliminated my slip-ups.
Although I use both hand calls and an e-caller, I am finding myself using my e-caller with its 24 bit technology more and more these days.
Castrating bands work great on open reed calls. Just roll one over the reed and your ready to go. They have many uses, like making up shooting sticks. They are easy to install, especially if you have the pliers for instalation. The last ones I bought were $1.99 for 100, so they won't break the bank.
I like my e-calls and have been using them for years! (MOF I wore out a couple of the old Johnny Stewart 512's) They are especially handy when hunting alone, because it gives me more time to glass the area. For years I used my mouth calls early and once I hit 4 or 5 stands I would go with the E-. More relaxed type of hunting and like you I just got tuckered out blowing lots of air thru my calls. IMI (in my imagination)
the E-call will be more effective later in the day than a mouth call will.
Talking about using lots of air calling..................I fill the air chamber of my open reed calls with epoxy. Then add a big match stick, after its dry I remove the match stick and I have a better air canal. If its too small I take a file and make the groove a bit bigger. This will use alot less air..........but it also makes the call a bit higher pitched and not quite as loud.
The Great Outdoors: Hunting