Our beauty regimen. It’s a girl’s best friend on days when we need that extra boost of confidence.But it can also be our worst enemy when we find that our perfect lipgloss/moisturizer/perfume is costing us more than a pretty penny—and according to a 2009 report, the average American woman shells out more than $100 a month on cosmetics.So, when we say we like our regimen to be as effective as possible, we mean cost-effective, too. Here are our favorite tips on making your beauty favorites last … and last.Less Is MorePortion control applies to hair products, too: You only need a quarter-sized dollop of shampoo, and a nickel-sized dose of conditioner (concentrate on the ends, not your scalp). If you’re at the tail end of a bottle, add a little water to it and the rest will come out more easily, suggests Jamie Allison Sanders of The Beauty of Life. And, when it comes to soap, don’t lather up every square inch of your body—lather just those areas that get sweaty or trap odor—especially since soap can dry your skin out.Read on for how getting dirty can save you even more money.Air Is the EnemyFood gets spoiled when exposed to air—the same goes for your beauty products. When possible, purchase pump bottles or squeeze tubes instead of lids or tops that open up. When something does comes in a pot or jar, put the lid back on right away to keep it from drying out or getting dirt in it.  A Second Shift for MakeupLet your lipstick work double-duty as cream blush, says Paige Herman-Axel of InsiderBeautyBuzz. Just about any color can be blended onto the apples of the cheeks for a long-lasting pop of color. And you’ll save money by letting a product do twice the work for the same price.MORE FROM LEARNVEST: Guide to the Best Non-Toxic MakeupIt Ain’t Over ‘Til It’s OverIt’s sad—not to mention expensive—to run out of a product you love. A lipstick brush will help you dig the very last color out of that favorite tube. The bottom of the lotion bottle pump can be handy for scraping the sides to unearth that extra ounce of body cream. And, says Sanders, try cutting a near-empty tube of product in half and using a makeup brush to transfer what’s left into a small, clean, jar with a lid to buy you a few days’ more bang for your buck.Don’t Neglect Your BrushesMakeup brushes are expensive. They’ll last longer—and work better—if you keep them clean. One helpful makeup artist we worked with told us not to blow on our brushes to rid them of excess product, because that covers them with bacteria from our mouths. Instead, she said, tap the side of the handle against your wrist to shake off any excess. Also, once a month, gently wash the bristles in baby shampoo, reshape and lay flat on a clean towel to dry.Give Cotton Balls the BootSurprise! You’ll shell out more using cotton balls. The fluffy orbs tend to absorb more product (and drip), meaning you wind up using more product in the process. We like  (80 for $2.29—less than three cents per pad), but Shannon Nelson of A Girl’s Gotta Spa swears that splurging on Renée Rouleau’s Toning Cloths (160 for $12.50, almost eight cents per cloth) will actually save you money. The thin, cotton pads absorb 50% less product and, because they’re easy to wield, do a better job of removing those last traces of nail polish or makeup residue.Cut Your Facial Wipes in HalfWe’ve been known to double the life of our pre-moistened wipes (like the ones for acne treatment or makeup remover) by cutting them in half. We even suggest letting any excess product drip off the wipes back into the jar first before using them, then using those above-mentioned toning cloths to soak up any product that remains once the wipes run out.MORE FROM LEARNVEST: Want Green, Safe Skincare?Maximize Your ManicureGet a longer-lasting manicure by applying a layer of top coat the day or two after you get them done, says Herman-Axel. And you already know that wearing rubber gloves when cleaning or doing dishes makes a world of difference, right?Keep Nail Polish WorkingIf you’re DIY-ing your manicure, store your nail polish in the fridge to extend its shelf life. If it gets too thick, use nail polish thinner. To make your manicure last longer, saving you polish in the process, dip your nails in white or apple cider vinegar and allow them to dry before you apply your base coat. The vinegar will remove the natural oils from your nails, allowing the polish to adhere better.Use Sense With Your ScentsThe average shelf life of perfume is two years, but if you’re careful, it can last longer. Keep it in a cool, dry place (like a drawer or closet) since sunlight can cause the scent to sour, and never in the bathroom where heat from the shower can lead it to oxidize. Seal your bottle after each use since alcohols in the fragrance dissolve when exposed to air. Finally, buy a small bottle, instead of a big one: Besides being cheaper, it’s less likely to go bad.MORE FROM LEARNVEST: Kick These Bad Habits … Before You Regret Them Later.