The Age of Consecration
"This is what concerns the Levites. From the age of twenty-five and upward, every Levite shall enter the service of the Tent of Meeting to serve. From the age of fifty, he shall leave office, and serve no more." (Numbers 8:24 - 25)
The enumeration of the children of Israel was intended to organize the people efficiently. The tribe of Levi was exempt from the counting, as it had a special status.
The Lord had chosen the Levites to be consecrated to Him alone in the service of the temple and for the transport and maintenance of the ark of the covenant. The Levites thus took the place of the first-born of the children of Israel before the Lord, because all the first-born belonged to Him for the service of the temple.
Note here the age required to begin service: 25. This was also the age to be counted among the men in Israel. The age at which the Levi had to stop service was 50.
What we need to understand here is that, when a person accepts Christ at the age of 40, he or she probably won't have the same faith as someone who accepted Him at 20. Faith is a life of experimentation, and the more trials you go through, the more it grows.
We are advised to seek consecration early in order to reach a high level of faith and knowledge of the Lord and His love. The later we do it, the more partial knowledge and partial commitment we will have, as if it were a burden.
P. Clémentine