It seems like shares of Tesla Motors Inc TSLA just won't quit, but some think it's time for investors to slow downTesla Motors Inc ( TSLA) shares have been back on a tear over the last several months, rising by 80% year to date and hovering near their all-time high. Meanwhile the broader stock market has stalled and begun to slump today, especially after the latest news out of Ukraine, although Tesla is down just .3% as of this writing. So is this the time to keep hitting the gas on Tesla stock, or is it time to let off the accelerator? As always, it depends on who you ask. Why Tesla stock has momentum So why have investors been snatching up shares of Tesla Motors like they’re going out of style? Fortune’s Alex Taylor III offers a few reasons, like the fact that the automaker’s running a hot and heavy competition among a handful of states about where it will put its gigafactory. In addition, Tesla’s order backlog is up to $226 million. With a production rate of 1,000 cars per week, which management expects by the end of this year, that amount will keep the automaker filling orders for 30 weeks without even accepting any more orders. In addition, Tesla Motors Inc ( TSLA) says its sales per square foot in its showrooms are twice that of Apple Inc. ( AAPL). Trouble ahead for Tesla? The problem, however, is that bears think Tesla stock is already priced as if it is selling hundreds of thousands of cars annually. The article in Fortune puts this into perspective: investors are valuing every car the automaker sells at $1 million. So Wall Street is also banking on the automaker delivering on its promises years into the future—so much so that Tesla’s promises are worth more than real results from other luxury automakers.