Do you want leaders in your church who are fresh and full of spiritual vitality? If so, here is the primary biblical principle for ensuring it happens: honour them.
We see that in 1 Timothy 5:17:
The elders who direct the affairs of the church well are worthy of double honour, especially those whose work is preaching and teaching
We see something similar in 1 Thessalonians 5:12:
In a related pasage (Heb. 13:7) the leaders (same word as in 1 Tim. and 1 Thess.) are the ones who spoke the word of God to you and who keep watch over your souls. It says we are to consider their life and faith and obey them as a joy, submitting to their authority.
Now we ask you, brothers to respect thsoe who work hard among you, who are over you in the Lord and who admonish you. Hold them in highest regard in love because of their work
The reason we are to obey leaders is because they keep watch over our souls by speaking the word of God to us. The authority with which they speak is the word of God. That is why Paul says that elders who preach and teach are worthy of double honour - they have an aweful, terrible, glorious task in the church.
Whenever I see a worn-out, burnt-out Christian leader, I will give odds of 10 to 1 that their church rarely thinks about honouring them, submitting to them, following them or obeying them. It's more likely that they will have been resisted, criticised or poorly paid. It's likely that they will have had their godly dreams for the church expunged by committees or church-meetings that think that democratic caution, rather than following leaders, is the way to go in church.
If, in your church, you never ask the question "how are we honouring our leaders?" then maybe you aren't. And maybe you are heading for leadership burnout. Maybe not this year or the next but with ever-growing likelihood for five or ten years time.
Do you want leaders who are fresh, who keep pressing on, loving the Lord, loving the church and loving leading? Then:
...make their work a joy, not a burden, for that would be of no advantage to you. (Heb 13:17)