United is currently offering a 40% discount on purchased miles through September 19, 2012. They’ve run this promotion in the past (and I’ve written with my thoughts on it), but I’ll recap it again since I’ve been getting a lot of reader emails whether this promotion is worth it or not.Promotion Landing Page With Links to Purchase MilesI personally value United miles higher than any other airline mileage currency. They aren’t perfect, but they are extremely valuable because there are so many partners and united.com actually shows a lot of partner availability, which saves me time having to call in. Their fees are low and they don’t charge fuel surcharges like some of their Star Alliance friends like Aeroplan. Plus, they are an instant 1:1 transfer partner of Chase Ultimate Rewards so its easy to top up my balance when needed.So all that being said, would I pay almost 2.3 cents to buy United miles? Personally, no because I have enough Chase points through my credit card sign-up bonuses so I’d rather keep my cash and use the points and miles I already have. However, that doesn’t mean it can’t make a lot of sense to buy them:1) If you need to top up your account for an award and you don’t have any Chase points (or prefer to use your Chase points on other valuable transfer partners like Hyatt).2) You redeem your United miles for awards that give you a value of greater than 2.3 cents. For example, if you’d pay $3,500 for a business class roundtrip ticket to Europe, then buying 100,000 miles for $2,257.50 might make a whole lot of sense. On the flip side, it would be like paying $575 for an economy class doemstic ticket- probably not worth it- especially since you don’t earn miles or elite status on award tickets.Offer details:To take advantage of this offer, you must use the order links on this page.For a limited time, save 20% off the regular price on purchases of less than 30,000 award miles, save 40% off the regular price on purchases of 30,000 award miles or moreBuy Personal Miles or Give Miles for less - only $28 per 1,000 miles when buying less than 30,000 award miles or only $21 per 1,000 miles when buying 30,000 or more award miles (normally $35 per 1,000 miles) plus a 7.5% excise tax for a limited time2,000 mile minimum purchase required and after that miles are available in increments of 1,000Discount can be used multiple times while the promotion is validPromotional offer valid until 11:59 p.m. CDT on September 19, 2012Purchase up to 100,000 MileagePlus Personal miles or Give Miles per account per calendar yearCredit card will be billed immediately for purchaseProgram fees and mileage rates subject to changeDiscounted pricing will automatically display when using the links on this pageAllow 48 hours for miles to post to MileagePlus® accountPersonal Miles and Give Miles are non-refundableThese miles can only be used for awards and do not count toward Premier® statusIf you have questions or concerns about this offer, please email custserv@ualmiles.com for assistanceAll MileagePlus Program Rules and terms and conditions apply[card card-name=‘Chase Sapphire Preferred® Card’ card-id=‘22125056’ type=‘javascript’ bullet-id=‘1’]Sign up for our daily newsletterEmail addressSign upI would like to subscribe to The Points Guy newsletters and special email promotions. The Points Guy will not share or sell your email. See privacy policy.