He should be putting more into his 401k...
There are annual caps on a 401. Most folks try to spread the contribution throughout the year instead of a lump sum.
No, the max contribution this year is $18,000 for people under 50. He is putting in $3000 a month. So assuming he is paid April-September, he will max out at the end of the season.
As someone at the site said for his 6 month season he puts in the max for his two week check of $1500. He has 26 pay periods. That is $18000.