What is your requirements to store the logs, especially for 5 years? SQL can certainly do it with the correct configuration but it's hard to make recommendations without knowing the scale required. We average between 5 and 8 billion logs yearly, at the standard message size(1k) it's a fairly large datastore. Since we have a lot of Windows event logs that can be 2k or more our storage would be 2.5-3x that.
If the goal is to search the logs at some future date what would be the most likely time window used? Weekly, monthly? I'd create my tables based on that, probably monthly.
Do you need SQL? Can the requirements be met with simple filesystem search? Or would it be better to use something like ElasticSearch?