Some of you may have read an article about how advertisements that are annoying are actually more effective. This can be true for establishing name recognition for a new product or business, or for reinforcing it in an older product like laundry detergent where a customer has to make a purchase decision while looking at a wall full of similar products in a super market. Chances are if you're running a gaming podcast that your advertisers aren't selling products that you buy in the super market.
There's a point at which repetitive advertising actually starts to have a negative effect. Either it actively causes customers to associate "don't like" with your sponsor, or else they simply stop listening to the podcast due to the repetition (perhaps as a contributing rather than a primary factor), at which point they hear neither you nor your sponsors.
So what's too much repetition? For starters, if you simply read or ad-lib a short script you're probably OK. The natural variation in tone between readings can help to mitigate the negative aspects of repetition, even if the words are exactly the same. This assumes that it is truly a short script. Under fifteen seconds is ideal, over thirty is generally unacceptable. If you want to run an infomercial for your sponsor do it once, not every episode.
If you pre-record your ads then for the sake of both your listeners and your sponsors change them every once in a while! How often you do so can vary, but one hard and fast rule is that if a date is mentioned in the ad, and it's past that date, then you should change the ad! That's the most obvious subset of a larger rule: if the ad is inaccurate, then change the ad!
Two examples from podcasts that will remain nameless:
1) An advertisement for a piece of software that was to undergo an update in a few months began running on a podcast. That same ad was still running a year after the updates had been made, but the ad still referred to those updates in the future tense.
2) An advertisement for a podcast that aired for quite some time on another podcast. It mentioned the hosts of the show. The ad was still running well over a year after one of the hosts had left the show and been replaced.
In the latter case the ad was created by the sponsor, so it may have been the case that they asked for a new spot and never received it, but they may have simply never bothered to ask.
Here's another rule of thumb: if you're mocking your own ads, then it's probably time to change them. Doubly so if you're mocking them on the show!
A tip for those who like pre-recording their ads: If you really want to pre-record your ads, and don't want to have to come back and change them very often, then record more than one at a time. Record two or three for one sponsor and then alternate them between shows. Having to listen to the same ad every second or third episode is far more tolerable than every episode. If you podcast frequently, once a week or more, then consider not just rotating ads, but rotating sponsors. Of course, you need multiple sponsors for this to work, and it has to be a part of whatever contract you have with your sponsors, but it can be extremely effective at reducing the negative effects of repetition.
So where do I get off offering this advice? Mostly just as an interested consumer, but I do actually have some limited experience writing ad copy for radio professionally, and received some equally limited education on the subject back in my college days. Take that for what it's worth.
I also want to say that I realize that podcasters do this for the love of their hobby and of podcasting, and that for the most part it costs them money out of their own pocket to do it, even with sponsors. I appreciate their efforts. I offer this advice both with the hope of making their shows better and to help their sponsors get better value for their sponsorship.