The number of spare strings you should have depends on your playing frequency and needs.
Professional or Student Musicians: If you play regularly, maintaining a few sets of backup strings in various materials is advisable. This ensures you're prepared for any situation and allows you to experiment with different string types to find your preferred sound.
Casual Players: For those who play occasionally, keeping a single spare set may suffice, as strings degrade primarily through consistent use and tuning.
E String Consideration: The E string is notably thin and more susceptible to breaking. Many musicians choose to stock additional E strings for this reason.
Storage Tips:
- Moderation: Avoid overstocking, as strings can deteriorate over time. Plan to use or replace any spares within 2-3 years.
- Cost-Effectiveness: Unless replacing a specific set, opt for reasonably priced strings rather than premium ones that might remain unused.
Ultimately, the quantity of spare strings you keep should align with your playing habits and the likelihood of string breakage. Assess your individual needs to ensure you're adequately prepared without unnecessary excess.