Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of vacation services provider Interval Leisure Group (Nasdaq: IILG) were enjoying a sunny day today, climbing as much as 15% in intraday trading after the company reported first-quarter results.

So what: As put by Interval CEO Craig Nash, "Interval Leisure Group started 2012 with success at every level." That sounds like great news and the numbers back up that assessment. Total revenue for the quarter increased 8.3% from a year ago to $127 million, above the $123 million that analysts were looking for. Earnings per share, meanwhile, were up 17% year over year and the $0.27 tally matched expectations. The year-over-year growth was driven by a 1.5% increase in active members and a 4.4% gain in revenue per member.

Now what: Shares of Interval are -- as of this writing -- changing hands at roughly 24 times expected 2012 earnings and 18 times estimated 2013 earnings. In other words, to consider this stock cheap, or even fairly priced, you have to assume some pretty robust growth ahead. The business seems to be doing quite well, but I'll admit to being skeptical that it will live up to those lofty assumptions.

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