I have a couple of Drachm and a Tetradrachm. Not sure how you tell if they are life time or not. These are two in my collection
A quick tip I've learned, as a general rule of thumb, is that if the reverse shows Zeus with his legs crossed (as with both of your coins) it is pretty much guaranteed to be a posthumous issue. If the legs are straight and parallel, then it's more likely to be a lifetime coin. Why this should be the case I'm not sure. Your best bet would be to verify attribution and go with whatever the reference catalog says (usually Price.)
Thanks. Are the lifetime issues more rare or are they just not sold off as much as the posthumous issues?
Some of both, but mostly the former. Those types were struck for only a decade or so under Alexander before he died, but continued to be issued posthumously for at least a century after his death.
There are features that tend to be found on posthumous or lifetime issues, some more reliable than others, but to be sure you need to identify each coin to the "Price #" (for Martin Price's standard reference). (There are exceptions to the crossed/uncrossed legs, BASILEUS legend, and monograms in fields as indicators. Though giant 32-35mm spread flan tetradrachms always mean late posthumous, since that was a later Hellenistic development.) The book is expensive so most people compare to sale records (e.g., acsearch.info) or use the American Numismatic Society's PELLA site, organized by Price #, and which gives a date range for each coin: https://numismatics.org/pella/ Alexander's lifetime ones aren't rare, but there are fewer since the posthumous ones were struck for centuries after his death and consequently very common (as a whole). Lifetime Drachms (and fractions) seem a bit more common, since they weren't struck quite as much posthumously. Note also, there are lots of "possible lifetime" issues (e.g., dated circa 325-320 BCE).
