Progressive's profit engine looks built for the long haul -- and today's valuation gives investors a reasonable entry point.Progressive's (PGR 0.24%) business has been on a tear as the auto and property insurer capitalizes on firm pricing and steady claim frequency. The company, the second-largest personal auto insurer in the U.S., continues to post strong growth while maintaining underwriting profitability well within its long-term target. But the stock has been in the doldrums. That combination of outstan ...