Without SLAs, vendor response is best-effort and varies wildly between Monday morning and Friday night. With them, you have a contractual baseline — and a record of breaches you can use to renegotiate or replace the vendor.
Realistic SLA targets for QSR refrigeration: 2-hour response, 4-hour first-time fix on common faults, 24-hour fix on parts-blocked repairs. For fryers and ovens, push for 4-hour response. Anything more lenient is a vendor problem dressed as a contract.