From the website for anybody who needs to know ingredients:

The active ingredient is estradiol enanthate (400 mg). Inactive ingredients are benzyl alcohol (2% w/w) as a preservative and MCT Oil as the carrier. Does not contain benzyl benzoate.

Edit: My quick internet search can’t find any studies looking at pharmaceutical use past 28 days. I remember reading a super informative post about benzyl alcohol a long time ago.

Since you’re talking about using it for longer than 30 days, I’d store it in an air tight container in the dark and toss in oxygen reducing packets to eat up all the oxygen in the container. Benzyl alcohol & estradiol both oxidize anyways.

Edit 2: @sidalsolgun@lemmy.ca quotes https://pghrt.diy/#S5.SS24

5.24 How long until a vial expires?

A sealed vial could last for years without issue if it is stored at stable temperatures away from the light. Concerns with age are primarily carrier oil oxidation assuming that the vial was sterilized as it should be. A punctured vial that has a preservative in it (see Question 6.17) should last at least a year or whatever the life time of the vial is (i.e., how long until you use it all). The “discard after 28 days” listing on vials is simply the minimum requirement for how long manufacturers must guarantee sterility, not the maximum shelf life.