i have done a few over the years- in ways they are a good way to go---one block to deal with a month- some shops have a set send date and charge your credit card the same time each month- others tend to send them out---when ever each month---and also charge your card....whenever
be prepared to pay about $300-$400 by the end of the program to do a quilt that way-
if you feel that is ok for 12 blocks....
also= if you have any problems putting your block together- or with being shorted in your kit- you have delays- sometimes additional charges- and no one to show you how to do what you are having problems with.
they certainly have their pros and cons....
if you choose to do one- choose a shop that has been around a long time- has a track record- and i prefer the shops that do not charge an extra (sign up fee) on top of the cost of the monthly blocks + shipping
be sure and find out about finishing kits---sometimes you think it's not so bad---$24.95 per month + shipping could easily already cost you $360 then at the end you get a package with border/binding fabrics and another $100 charge!
read the fine print- make sure you know what you are getting yourself into-
and remember it is a year long commitment- they will not willingly allow you to drop out part way through- they will charge you for the whole program!
for your first bom you might want to find a local shop doing one and start there.