First up, it is worth mentioning that the e-card is the front side of the card, and the back relates to the EHIC (German: EKVK). The use of the EHIC card issued from Austria depends on the amount of time you have been making statutory healthcare contributions (usually deducted at source from your salary if you are employed, or through your monthly or quarterly payments to the SVS for self-employed).
The validity of the EHIC on the back depends on how long you have been insured and paying contributions for (“in einer Krankenversicherung pflichtversichert”) at the cut-off date for the card being issued. A validity of one year means that you have, from the records held, been insured for at least one out of the last five years and at least 180 days in the last year. You will be issued a five year card if you have been insured for five out of the past ten years prior to the card being issued and at least 180 days in the last year.