Longevity means that the elderly live longer and are healthy.
For example, the word "happiness as the East China Sea" means longevity. Use mountains and seas to describe longevity.
It is also exquisite to use seal script instead of other fonts. Seal script is an early font in China, and it is the earliest of the five major fonts in China (seal script, official script, regular script, running script and cursive script). Compared with other fonts, it has an older history and a long meaning.
And in the form of calligraphy works, it inherits China's Confucianism, with Confucian style in it.
In a word, blessing, longevity, seal script and calligraphy all reflect the good intentions of the old man's blessing. This is a good gift form.
I hope I can help you, thank you!