Illustrator is notorious for getting exceptionally slow once you pass some [hidden and unknown] object limit. It's been a stable of the application since it was created (seriously, since version 1.1) and has never really been addressed by Adobe. In fact, they tend to deny it but users know better.
I would create a Pattern Swatch for the type. After all, it is merely a repeating pattern...
- Set Type
- Drag type to Swatch Panel to create a Pattern Swatch
- Double-click new Pattern swatch to adjust the tile size and configuration
(brick by row for example to offset lines from one another)
- Add a new fill to a shape and apply the pattern. In some cases merely altering the blending mode may be sufficient.
Type is still live. So you can merely double-click the pattern swatch at any time and change the type...
If you want the opposing gradients, one in the base shape, then an opposite or different gradient for the type, I'd use this pattern set up combined with an Opacity Mask.
Create two shapes stacked on top of one another...
Select and copy the top shape.
With the top shape selected, click the
Make Mask button on the Transparency Panel. This will create a little black box for the mask on the panel, click the black box... And then
Edit > Paste in Front to paste your top shape onto the mask.
Now merely change the fill to your pattern and tick the
Invert Mask box on the panel.
You then have to click the artwork thumbnail on the Transparency panel to go back to editing the artwork.
If the two shapes are the same, there's the appearance of seamless integration...
Because this uses a pattern, there is only one object for AI to track — that original type object in the pattern. It sees only a single object, then merely creates data points back to that one object. There's no way you'll hit that invisible, unknown object limit with a pattern (unless the initial pattern object itself is overly complex).