Stamp collectors have the stuff and the somethings that are similar to securities (issued, as they are by governments) and provide liquidity as they are salable at a moment's notice to a ready and enthusiastic clientele.
But don't forget that the sale of your stamps is dependent upon many things. Condition, rarity, demand (are they scarce enough to be strongly sought after?), as well as other considerations, will all affect your success when you go to sell.
Avoid a Mish-Mosh Stamp Accumulation
One important factor that is often overlooked by the collector is organization. If you've been more a hoarder (perhaps more correctly an accumulator when one speaks of stamps) it might have a real impact on your reselling success. After all, if a buyer can't see your material, on what can he base his offer to you?
Especially when you try to sell to stamp dealers, you must make sure everything is there to be easily seen. If it is otherwise, any premium items hidden in the mix will potentially be missed and uncounted. (This applies to bulk stamps and covers, packed in boxes and bags, what old-time dealers one called mish-mosh. On the other hand, if you are offering stamps in albums I assume you know what's in them, and can point out better items to a dealer, so he offers a better price.)
A Famous Stamp Accumulator
There have been accumulators of note, among them Colonel E.H.R. Green, son of Hetty Green, the so-called Witch of Wall Street. With his remarkable wealth, he is said to have bought the entire stock of stamp stores on the spot. His appearance on Nassau Street in NYC, the center of stamp dealing for many years, would send dealers to their vaults to get out their finest material for Green to consider. Today he is best known as the buyer of the Inverted Jenny sheet, or as most non-collectors know it, the upside-down airplane stamp.
Green's accumulation, when sold at auction, was featured in multiple sessions and realized stunning prices. The material's realizations were somewhat based -- beyond what the philatelic items may have been worth according to the catalog value -- on the fame of the former owner, a true star in the philatelic world at the time.
The Allure of Unorganized Stamps
If you are trying to sell to other collectors sometimes a messy lot of stamps and covers can do quite well. You can find ads in the philatelic press and online for Mystery Lots and Unsearched Collections. Part of the hype is that these are unsearched and that the buyer has an opportunity to find a treasure. Just don't forget the expression "One person's treasure is another's trash" and consider what you're going in for when you purchase a Mystery Lot.
Even if they are over-hyped they are yet another pleasure of the hobby. And yes, sometimes one can find an item that is far from a treasure but can nevertheless be of enough value that it alone can make the experience worthwhile.
Clean Up a Family Stamp Collection
When all is said and done, there are times of financial trouble, such as we are currently going through, when interest in simpler and cheaper pastimes is always welcome. Those who have an untended stamp collection in the family may go to the closet and get it out. They may consider their options -- some may take up the hobby.
But with the price of a movie and its ephemeral entertainment, the relatively inexpensive cost of stamps may start to look like an option for a pleasant diversion. But if no one is interested in taking up the hobby, there should be no compunction in selling and tipping your hat to grandpa -- or whoever it originally belonged to -- in thanks for the windfall.
If it is not in the best state of the organization, you'll be doing yourself a favor by cleaning it up, making sure it has a good appearance, with the stamps well organized properly placed in the album, whether on pre-printed pages or arranged logically by country or topic in a stock book. Doing so will prove to be well worth your time.