This is actually a very common question which every blogger thinks about every once in a while. The truth is nothing is forever. What goes up must come down. There is always a start and an end. The question is how long it will last? How long can you keep on blogging until you really finish all the topics that you can possible write about? In order to survive and keeps on making money online, you just have to extend the number of topics that you are going to blog. So how do you extend the topics? Just pick an old topic or blog post that you covered before and try to break it into several small topics. Basically you are actually extending the topics by going into details of every step. Take for example of the topics of pursuit for money making opportunities online. Your main topics are usually about methods or ways to make money online. Regardless of the main topics, you can try to go into other related details such as type of customers that you target, the payment methods, the banks to draw money, the currency that you need to convert, the tax involve, the tools that you are using, the computer hardware that you are using, alternative investment, the online safety issues, the security issues, the software utilize, the mentor, other offline business comparison, the lifestyle of entrepreneur, etc.
If you really go into details, there are millions of topics that you can blog about. So it should be enough for you to blog about for the rest of your life. The problem that you might be facing is that not every topic can help you make money online. Unfortunately most of us do not know if the topic can really draws money until we post it out. So the best way is to write as many blog posts as possible and hope for the best. But I think you should be able to make some money over time as long as you keep on blogging.