You will find that not everyone on your list will buy a product every single time so your blog business will depend on the law of averages. The larger the number the more chances of you receiving a sale. Of course you also need to factor in your relationship with that list and the product you are offering but most professional bloggers focus on continually building their list because of the law of averages.
If you have a list of 10,000 and 10% buy a product that is great, but if you have a list of 80,000 and 10% buy a product that is even better! This is why encouraging people to opt-in to continue hearing from you is important because not everyone will buy immediately and some people never
Your List Is Your Bottom Line, Respect It
When all is said and done your list will keep you earning money for as long as you want it to so look after your subscribers and treat them with respect. If you start sending out content that is below par they will just hit the unsubscribe button. If you make it difficult for them to unsubcribe
you will end up in the spam box! Give people a good reason to stay by providing ongoing valuable content mixed in with the odd promotion here and there for a product.