There are currently 3 types of Strong Nodes and each one has a different duration
First things first though. I assume you know that Strong has transitioned to Stronger. If that is news to you then you have some homework to do. Please check out my Strong Coin explanation to get a better sense of what this project is about.
Ethereum Strong nodes expiration
Strong nodes for Ethereum last 266 days. You invest 10 STRNGR to set up an Ethereum node and receive 0.075 STRNGR per day until your total rewards reach 20 STRNGR. After that, your Strong node expires and you need to start anew. That means your nodes will last 9 months if you set them up on Ethereum.
Keep in mind that StrongBlock can update the rewards at any time.
For example, ETH Strong node rewards used to be 0.091 STRNGR per day so you will find most other sources claiming ETH Strong nodes will last 6-7 months.
If you want to cross verify check the official StrongBlock site for Ethereum node rewards
Also, keep in mind that you are responsible for covering the monthly maintenance fees which stand at $14.95. If you do cover the maintenance fee within 30 days your node is terminated after day 30.
Fantom Strong nodes duration
With Fantom nodes reward you 0.075 STRNGR per day with an 18 STRNGR maximum. This means that your Strong nodes will last 18/0.075=240 which is almost 8 months.
After your nodes die you can start anew if you like. I am not sure you should do this though. Check out my article is Strong Coin a good investment to learn more.
Polygon Strong nodes
The Strong nodes for Polygon use a strange tapering reward system. I don’t know why they do this as it makes calculations confusing. The maximum reward you can earn through a Polygon Strong node is 36 STRNGR. Here is how it works. In month 1, you get 3.6 STRNGR. Then in Month 2 a little less. In month 3 even less and so on. The total life span of Polygon Strong nodes is 40 months after which they are retired.
Please comment below in case you have any questions. I respond fast. If you want to estimate your reward ( or losses more likely) check out my strong node calculator.