I am having 12% per week taken out of my pay for my 401k with MFS. I just discovered that my company only buys shares of our MFS funds every quarter. Is this normal and am I losing out this way? and would I be better off investing a portion of that money on a weekly basis on a seperate IRA?

I feel like I could have that money working for me for that quarter instead of it siting with my company before they send it to MFS.

Thanks
Rob