This depends on your business needs, but a good rule of thumb is probably to split your savings between easy access and fixed rate accounts. The benefit of locking your money away is that you'll get more interest, and generally speaking, the longer the term, the higher the rate.
This means you have the potential to get a substantial return from your surplus cash by the end of the term, but just bear in mind that fixed rate accounts typically won't allow access prior to maturity (and if they do, there could be a hefty penalty), so you'll need to be confident that you won't need access to your money for the duration of the deal.
This is why you'll want to keep at least a portion of your savings in a more accessible account, to ensure you can withdraw funds easily should you need them. These accounts will typically be variable rate, which means they could change at any time, but there are still some competitive deals available – particularly if you don't mind giving a bit of notice to access your funds.
Then there's the potential to lock your money away for only a very short period of time – this could still give you a better return than an easy access account, but you can be safe in the knowledge that you don't have to lose access for long. Some providers will offer fixed rate bonds with terms as short as three or six months, which could be the ideal compromise for some businesses.