enter code hereIt took me a long long time to figure out whether getting the Lisboa Card was worth it for me and my spouse. We aren't senior citizens though, but I think this technique may help you. I don't know why it took me so long to figure it out, but this technique, if you haven't figured it out already, is like a "Duh!" :)
So here goes:
1) Download the Lisboa Card pamphlet which tells you which sites/activities are discounted or free.
Go to this weblink and then click on the "Lisboa Card Guide" button: https://www.visitlisboa.com/en/p/lisboa-card
Or, just go directly to the guide here: https://cdn.shopify.com/s/files/1/0397/6318/1732/files/Guia_LxCard_Ing_Esp.pdf?v=1680696476d_Ing_Esp.pdf?v=1680696476
And also download this Services and Discount List: https://cdn.shopify.com/s/files/1/0397/6318/1732/files/Lisboa_Card_Abril_2023_Ing.pdf?v=1680280003
The Services and Discount List gives a good summary and is the more useful one to help you make your determination.
2) Now, look at the Discount List and figure out which sites/activities you will "definitely" be visiting.
3) Now, go to each of those site's website and see how much it would cost you without the Card, and with the Card.
We figured out that by joining about 3 to 4 of the major sites that were "free" with the Card, we would have covered the cost for the 72 hour version of the card. (Don't quote me on that because my memory could be faulty and prices also could have changed).
So one way to try to expedite your decision process is just look at which of the "free" (with the Card) sites you will "definitely" go to and then compare the prices with and without the Card.
For our situation, it wasn't necessary to consider whether we would use enough transportation to cover the Lisboa Card because the sites we plan to go to already would have made the cost worth it.
Also, if you will be primarily engaged in transportation and not as many sites, it could be more worth your money to get things like day passes/pre-paid tickets instead of the Lisboa card. Public transportation in Lisbon, by middle-class North American standards, is really quite inexpensive. In fact, I'm amazed that it is that cheap to ride public transit in a major world city like Lisbon compared to the town I live in which is, at best, a regional city (not work city, not a capital). See: https://www.carris.pt/en/buy/occasional-journeys/
Note: it is more economical to purchase pre-paid tickets for Lisbon transportation instead of paying onboard for the various Trams in Lisbon. If I recall, if you pay when you board, it costs almost 3 Euros, but if you have a pre-paid ticket, the pre-paid ticket to ride a tram is just 1.60-ish Euros. As you know, if you have a Lisboa Card, it’ll cover transport. But there are other cards that are transport only.
Hope this all helps!