Job hunters are like houses waiting to be sold; the longer they are on the market, the harder it is to sell them. In the case of houses, real estate agents change their strategy or update a property's details (e.g. price, curb appeal, etc.) to generate leads. Similarly, you should make changes to garner a desirable offer sooner.
Start by making these three changes if any are applicable to you, switch:
1) from applying to firms without internal endorsements to using LinkedIn to find internal endorsers
2) from job-seeking without a team to enlisting brand advocates
3) from using the same interview approach and answers to seeking constructive feedback and acting upon it
Move quickly on these changes or you'll continue to depreciate in value.
Use LinkedIn - If you are blindly applying to jobs via sites like theladders.com then start incorporating LinkedIn and applying to jobs where you have relationships. Use LinkedIn to identify who can bring you closer to your target companies. Call this person. Ask them to not only hand deliver your marketing materials but also to endorse your candidacy. In most cases when a current employee is referring a job candidate the assumption is that this candidate is good; they are good enough for that employee to put his or her reputation on the table for them. Plus, there may also be a referral bonus in it for them, should you get hired.
Enlist brand advocates - If you are the only person actively working on your job hunt then it will persist longer than necessary. You need a team to motivate you, extend your reach, and prepare you for high stakes conversations. The better approach is to find and inform your professional "brand advocates." Once you find these individuals tell them that you'd like their help with your marketing efforts and give them the marketing materials they will need to easily do so. For instance, draft an email note detailing your top three major accomplishments that they can easily forward along to others. The key is making the act of marketing you as simple as hitting a "send" button.
Ask for a mock interview - If you have interviewed with many firms yet have not progressed beyond initial conversations than evaluate your interview approach as well as what you usually say in response to these key questions: 1) tell me about yourself, 2) what are your weaknesses, and 3) what can you do better than anyone else. An evaluation is only helpful if it is done by a subjective party that cares about your progress and if they are candid. Now, if you have zero candid friends then seek professional assistance from a coach.
If you feel that you have been in the job market for too long and you are losing steam then it's critical to reinvigorate your hunt by changing your strategy or stats (as a real estate agent would relative to a house that has been on the market for too long). The alternative is doing the same thing over and over and expecting different results which happens to be as Albert Einstein defined insanity.
How long are you willing to forgo that pay check? What's your magic number?