AutoZone (AZO) reported strong fiscal second-quarter 2012 results Tuesday that showed solid same-store-sales increases and bottom-line expansion. We’ll be tuning in to the firm’s conference call, but we don’t expect to make a change to our fair value estimate for the auto-parts retailer at this time. AutoZone’s fourth-quarter revenue advanced 8.6% during the period thanks to nearly a 6% increase in same-store-sales. Gross margin increased 40 basis points, to 51.3%, in the quarter, but such improved profitability was more than offset by higher self-insurance costs. The company’s net income jumped nearly 13% in the quarter, while diluted earnings per share of $4.15 increased over 24% from the same period a year ago thanks to share buybacks. Consensus was at $4.04 per share for the quarter, so the firm’s performance represented a material beat. Though AutoZone continues to reap the benefits of an aging