Signaling is important. The people who knock on your door on a rainy day are more committed than the ones who go around on a nice day. Pamphlets shoved under your windshield wiper show particular laziness. But what is being signaled may vary, too. If the religion is one that requires its members to go out knocking on doors, the same is likely in store for you if you convert.
The supply of potential converts is probably fairly stable. Some people are happy in their religion or lack thereof; others are not. Proselytization may be a race to find the ones who are questioning in their faith but haven’t taken many affirmative steps yet. Given the vast number of possible choices of possible new religions, one may be stuck in this state for some time. The first knock on the door will be taken as a sign. This phenomenon leads to wasteful racing behavior.
This last observation would suggest that if you aren’t in the market for a conversion experience, you should note that fact prominently so they’ll pass your house by. But, then again, given the nature of the task, the door-to-door teams may be rationally disinclined to ignore prominent religious symbols and ring the doorbell anyway. After all, many people in the relevant state of mind will be afraid to admit to themselves that they are, and therefore will be reluctant to remove symbols posted in an earlier attitude of confidence.
Extensive proselytization is a labor-intensive activity. Religions and sects that have large numbers of adherents relative to their wealth should be expected to engage in it more. Expect a shift to more capital-intensive forms of recruitment as wealth grows. Billboards and TV commercials are one technique; the Catholic approach of funding schools is another.