In the end, it's use it or lose it (same for recruiting dollars). That said, most folks will keep a certain dollar amount saved for when recruiting starts. If you find yourselves in several battles or higher division teams are on your players and it's unlikely you'll sign guys you targeted, having extra scouting dollars to find new players comes in handy.
And just an FYI-your scouting and recruiting budgets are fixed during the first recruiting period (RS1). After the season ends, when the second recruiting period begins (RS2), you can cut players you did not sign (so, those signed by the sim or another coach though, I wouldn't cut any of Arfy's old players) and get full scouting and recruiting dollars for each player cut.