Sure, but long term strategy at a 6 month old company is a year out. 2 years at best. 5 years is multiple lifetimes for most startups.
I think that's becoming an increasingly popular opinion, but I really don't buy into it. If you have one year of runway, certainly you should have a one year plan, but I like to see something longer term as well.
Every company/organization/person should have a long term strategy. That way you can weigh potential actions to see if they are moving you toward or away from your goal. If you don't have that goal, or it isn't well communicated, everyone scrambles to optimize for different things, which frequently leads to people pulling against each other.
It's totally acceptable to update the long term goal as you go along, but it's very helpful to always keep one in focus.