Paul says little about the spiritual requirements of elders in his first letter to Timothy (he has more to say to Titus on this topic). We may safely say, as John Stott observes, that he expected them to be truly converted believers - people who had made a sincere commitment to Christ and whose lives showed evidence of the fruit of the Spirit. But beyond that he has just one thing to say about their spirituality - they must not be recent converts, lest they become conceited and fall under the judgment as the devil (1 Timothy 3:6).
In itself, this is not a requirement that leaders in the church be men of "senior years." While it is true that elders in the first churches were probably men who were older in years as well as in spiritual experience, Paul's directive to Timothy doesn't say they have to be older in age. He simply says they must not be "recent converts", literally, "neophytes", those "newly planted in Christ" (Stott, p. 98).
The reason he gives for this is to safeguard a church leader against becoming conceited, and subsequently falling under the judgment of the devil. The term "conceited", Stott points out, is "a colourful verb meaning to 'becloud'" (p. 98). He notes that Paul uses it later to refer to false teachers (6:4), and suggests that it is meant to convey the idea of people living in "'cloud-cuckoo-land', a realm of self-centred fantasy" (p. 98). The danger is very real. All of us are prone to over-inflated notions of self-importance when we are appointed to positions of responsibility. That is all the more true when young or immature people are entrusted with places of authority usually reserved for those of greater wisdom and experience.
In that respect, it is interesting to reflect on the long-practiced pattern in Western churches of ordaining young men straight from theological colleges into pastoral leadership in churches. Men in their early to mid-twenties, often with little experience of life beyond educational institutions, are frequently thrust into positions of leadership in churches containing many Christians older and wiser than they are. Commenting on this practice, John Stott says that while it has "much to commend it," it also has its dangers "if they [the new ordinands] have had insufficient time since conversion to put down roots and to grow up in Christ" (p. 98). I personally find that it has little to commend it, and think it much wiser for younger men to use their acquired knowledge and skills in the context of a team of mature leaders who can guide, counsel and protect them. That way, they are much more likely to avoid falling prey to "self-centred fantasy".
Paul highlights the importance of avoiding this fault by warning that proud presbyters (elders, leaders) are liable to suffer the same judgment as the devil. While he doesn't say in so many words what that judgment was, we know all the same that it entailed Satan being "cast down" from his place of privilege and authority. Perhaps Paul is thinking of that in this connection. God sets his face against the proud and arrogant and invariably humbles such people (see James 4:6). Proud church leaders put themselves in the position of being judged by God and brought to nothing. History offers us too many examples to deny that this can happen.
That, by implication, makes humility an essential requirement for those who lead in the church. John Stott puts it well when he writes "humility is a necessary requirement for the pastorate, including humility before God in a life of personal devotion, faith and obedience" (p. 99). Whether older or younger in years, church leaders must be meek and humble men.