You don't have to sell the patent outright, another option is to license it. There may be some capitol gains tax advantages to this approach too.
As you mentioned, holding a patent doesn't guarantee protection. A Canadian company infringed on a US tool patent I held and sold their knock-offs in the US. This was about 14 years into the patent run. I had licensed a company to manufacture and market the tool, and they kindly sent me royalty checks. Doing battle would have likely cost at least $200K and would have meant defending on the east coast while I live in CA. The clincher was that my licensee really didn't want to do battle (he was responsible for 75% of the cost to defend) and it was felt that with the patent's age, and the minimal sales impact the infringer was making, it was a losing proposition.
All said, though, I disagree. If yours is a good idea and is not prior art . . . go for it. At least get the patent pending before going to market.
I've also licensed tool designs I didn't bother to patent (same mfg. as above), however they only paid me 1/2 the percentage they did on the patented tool.