A co-worker insists that it is better to spread contributions out over the entire year, so as "not to lose any of the employer match".

This is the case with my plan as well. My employer matches 1/2 of the first 6% of the employee contribution. This is done for each contribution, which occurs with each paycheck.

Contributing more than 6% in a given paycheck will not cause my employer to match any more than 3% for that paycheck. It will also not cause my employer to contribute any more than the 3% if I stop contributing for the year. In other words, the matching is done on a per-paycheck basis and there is no "annual" calculation that is done, other than the annual max for the employee contributions.

Therefore it behooves me to stretch my contributions out over the whole year, contributing at least 6% with every paycheck, in order to receive the full company match.

-progmtl.